Biochemical Engineering. BiologicalProcess. Definition of Fermentation. Problems. References. Chapter 2: Enzyme Kinetics. Introduction. PDF | Recent advances in biotechnology have enabled the development of products and The second edition of Biochemical Engineering and. The role of biochemical engineering in biotechnology, as the technology of considerations, to impart a flavour of the biochemical engineering activities and.

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A survey of biochemical engineering in Britain has been carried out on behalf of the. Science Research Council's Chemical Engineering and Technology. Bailey, J. E., and D. F. Ollis, Biochemical Engineering Fundamentals, 2d Vogel, H. C., Fermentation and Biochemical Engineering Handbook: Prin- ciples. CHEMICAL. ENGINEERING AT. CBU. A Chemical Engineering degree from CBU will provide you with the tools and practical problem-solving skills you need to.

Biotechnology[ edit ] Biotechnology and biochemical engineering are closely related to each other as biochemical engineering can be considered a sub-branch of biotechnology. One of the primary focuses of biotechnology is in the medical field, where biochemical engineers work to design pharmaceuticals, artificial organs, biomedical devices, chemical sensors, and drug delivery systems. Specific areas of studies include metabolic, enzyme, and tissue engineering. The study of cell cultures is widely used in biochemical engineering and biotechnology due to its many applications in developing natural fuels, improving the efficiency in producing drugs and pharmaceutical processes, and also creating cures for disease. Food Industry[ edit ] Biochemical engineers primarily focus on designing systems that will improve the production, processing, packaging, storage, and distribution of food. There are three levels of food processing: primary, secondary, and tertiary. Primary food processing involves turning agricultural products into other products that can be turned into food, secondary food processing is the making of food from readily available ingredients, and tertiary food processing is commercial production of ready-to eat or heat-and-serve foods. Drying, pickling, salting, and fermenting foods were some of the oldest food processing techniques used to preserve food by preventing yeasts, molds, and bacteria to cause spoiling. Biochemical engineers also work to improve the nutritional value of food products, such as in golden rice, which was developed to prevent vitamin A deficiency in certain areas where this was an issue. Efforts to advance preserving technologies can also ensure lasting retention of nutrients as foods are stored. Packaging plays a key role in preserving as well as ensuring the safety of the food by protecting the product from contamination, physical damage, and tampering. A common job for biochemical engineers working in the food industry is to design ways to perform all these processes on a large scale in order to meet the demands of the population.

Author Bios Prof. Katoh is an enthusiastic lecturer in Biochemical Engineering, Bioseparation Engineering and Immunotechnology. He is an outstanding expert in biochemical engineering and has published numerous papers in this field. Fumitake Yoshida was one of the world's most respected chemical engineers.

Most recently he was professor emeritus of chemical engineering at Kyoto University and well beyond his retirement he continued to be a visiting lecturer at universities around the world. He conducted research on various mass transfer operations, gas-liquid systems in particular, investigating their applications in bioengineering and medical technology. Among his many awards and citations was election to the National Academy of Engineering of the United States in for his leadership in chemical, biochemical, and biomedical engineering in Japan.

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The author will be responsible for the accuracy and completeness of the references. Liu, K. Specialty Chemicals amino acids, enzymes, vitamins, lipids, hydroxylated aromatics, biopolymers. Environmental Applications mineral leaching, metal concentration, pollution control, toxic waste degradation, and enhanced oil recovery. Commodity Chemicals acetic acid, acetone, butanol, ethanol, many other products from biomass conversion processes. Bioelectronics Biosensors, biochips. The fermentation will be stopped and the contents will be pumped out for the product recovery and purification.

This process can be operated either by batch or continuously. To carry out a bioprocess on a large scale, biochemical engineers need to work together with biological scientists: Similar techniques which have been working successfully in chemical processes can be employed with modifications.

The basic questions which need to be asked for the process development and design are as follows: What change can be expected to occur? To answer this question, one must have an understanding of the basic sciences for the process involved. These are microbiology, biochemistry, molecular biology, genetics, and so on. Biochemical engineers need to study these areas to a certain extent. It is also true that the contribution of biochemical engineers in selecting and developing the best biological catalyst is quite limited unless the engineer receives specialized training.

However, it is important for biochemical engineers to get involved in this stage, so that the biological catalyst may be selected or genetically modified with a consideration of the large-scale operation. Introduction 2. How fast will the process take place? If a certain process can produce a product, it is important to know how fast the process can take place.

Kinetics deals with rate of a reaction and how it is affected by various chemical and physical conditions. This is where the expertise of chemical engineers familiar with chemical kinetics and reactor design plays a major role. Similar techniques can be employed to deal with enzyme or cell kinetics. To design an effective bioreactor for the biological catalyst to perform, it is also important to know how the rate of the reaction is influenced by various operating conditions.

This involves the study of thermodynamics, transport phenomena, biological interactions, clonal stability, and so on. How can the system be operated and controlled for the maximum yield? For the optimum operation and control, reliable on-line sensing devices need to be developed. On-line optimization algorithms need to be developed and used to enhance the operability of bioprocess and to ensure that these processes are operated at the most economical points.

How can the products be separated with maximum purity and minimum costs? For this step, the downstream processing or bioseparation , a biochemical engineer can utilize various separation techniques developed in chemical processes such as distillation, absorption, extraction, adsorption, drying, filtration, precipitation, and leaching.

In addition to these standard separation techniques, the biochemical engineer needs to develop novel techniques which are suitable to separate the biological materials. Many techniques have been developed to separate or to analyze biological materials on a small laboratory scale, such as chromatography, electrophoresis, and dialysis.

These techniques need to be further developed so that they may be operated on a large industrial scale. Biological Process Industrial applications of biological processes are to use living cells or their components to effect desired physical or chemical changes.

Biological processes have advantages and disadvantages over traditional chemical processes. The major advantages are as follows: Mild reaction condition: The reaction conditions for bioprocesses are mild. The typical condition is at room temperature, atmospheric pressure, and fairly neutral medium pH. As a result, the operation is less hazardous, and the manufacturing facilities are less complex compared to typical chemical processes.

An enzyme catalyst is highly specific and catalyzes only one or a small number of chemical reactions. A great variety of enzymes exist that can catalyze a very wide range of reactions. The rate of an enzyme-catalyzed reaction is usually much faster than that of the same reaction when directed by nonbiological catalysts.

A small amount of enzyme is required to produce the desired effect. Renewable resources: The major raw material for bioprocesses is biomass which provides both the carbon skeletons and the energy required for synthesis for organic chemical manufacture. Recombinant DNA technology: The development of the recombinant DNA technology promises enormous possibilities to improve biological processes.

However, biological processes have the following disadvantages: Complex product mixtures: In cases of cell cultivation microbial, animal, or plant , multiple enzyme reactions are occurring in sequence or in parallel, the final product mixture contains cell mass, many metabolic by-products, and a remnant of the original nutrients.

The cell mass also contains various cell components. Dilute aqueous environments: The components of commercial interests are only produced in small amounts in an aqueous medium. Therefore, separation is very expensive. Since products of bioprocesses are frequently heat sensitive, traditional separation techniques cannot be employed.

Therefore, novel separation techniques that have been developed for analytical purposes, need to be scaled up. The fermenter system can be easily contaminated, since many environmental bacteria and molds grow well in most media. The problem becomes more difficult with the cultivation of plant or animal cells because their growth rates are much slower than those of environmental bacteria or molds.

Introduction 4. Cells tend to mutate due to the changing environment and may lose some characteristics vital for the success of process. Enzymes are comparatively sensitive or unstable molecules and require care in their use. Definition of Fermentation Traditionally, fermentation was defined as the process for the production of alcohol or lactic acid from glucose C6H12O6.

Problems 1. Bring a copy of the article and be ready to discuss or explain it during class. An International Analysis, p. Washington, DC: Office of Technology Assessment, Journals covering general areas of biotechnology and bioprocesses: Enzyme Kinetics 2. Simple Enzyme Kinetics Evaluation of Michaelis-Menten Parameters Enzyme Reactor with Simple Kinetics Inhibition of Enzyme Reactions Other Influences on Enzyme Activity Enzyme Kinetics Chapter 2.

Introduction Enzymes are biological catalysts that are protein molecules in nature. They are produced by living cells animal, plant, and microorganism and are absolutely essential as catalysts in biochemical reactions.

Almost every reaction in a cell requires the presence of a specific enzyme. A major function of enzymes in a living system is to catalyze the making and breaking of chemical bonds. Therefore, like any other catalysts, they increase the rate of reaction without themselves undergoing permanent chemical changes.

The catalytic ability of enzymes is due to its particular protein structure. A specific chemical reaction is catalyzed at a small portion of the surface of an enzyme, which is known as the active site. Some physical and chemical interactions occur at this site to catalyze a certain chemical reaction for a certain enzyme.

Enzyme reactions are different from chemical reactions, as follows: An enzyme catalyst is highly specific, and catalyzes only one or a small number of chemical reactions. A great variety of enzymes exist, which can catalyze a very wide range of reactions.

Only a small amount of enzyme is required to produce a desired effect. The reaction conditions temperature, pressure, pH, and so on for the enzyme reactions are very mild. Nomenclature of Enzymes Originally enzymes were given nondescriptive names such as: The new system categorizes all enzymes into six major classes depending on the general type of chemical reaction which they catalyze. Each main class contains subclasses, subsubclasses, and subsubsubclasses.

Therefore, each enzyme can be designated by a numerical code system. As an example, alcohol dehydrogenase is assigned as 1. Bohinski, Commercial Applications of Enzymes Enzymes have been used since early human history without knowledge of what they were or how they worked.

They were used for such things as making sweets from starch, clotting milk to make cheese, and brewing soy sauce. Enzymes have been utilized commercially since the s, when fungal cell extracts were first added to brewing vats to facilitate the breakdown of starch into sugars Eveleigh, The fungal amylase takadiastase was employed as a digestive aid in the United States as early as Enzyme Kinetics Table 2.

Oxidoreductases 1. Specific substrate is ethyl alcohol 2. Transferases 2. Transfer of methyl groups 2. Transfer of glycosyl groups 3.

200597572 Biochemical Engineering and Biotechnology Handbook ATKINSON

Hydrolases 4. Lyases 5. Isomerases 6. Ligases Example Reaction: Trivial Name: Enzymes are usually made by microorganisms grown in a pure culture or obtained directly from plants and animals.

The enzymes produced commercially can be classified into three major categories Crueger and Crueger, Industrial enzymes, such as amylases, proteases, glucose isomerase, lipase, catalases, and penicillin acylases 2. Analytical enzymes, such as glucose oxidase, galactose oxidase, alcohol dehydrogenase, hexokinase, muramidase, and cholesterol oxidase 3.

Alkaline protease is added to laundry detergents as a cleaning aid, and widely used in Western Europe. Proteins often precipitate on soiled clothes or make dirt adhere to the textile fibers. Such stains can be dissolved easily by addition of protease to the detergent.

Protease is also used for meat tenderizer and cheese making. The scale of application of analytical and medical enzymes is in the range of milligrams to grams while that of industrial enzymes is in tons. Analytical and medical enzymes are usually required to be in their pure forms; therefore, their production costs are high.

Simple Enzyme Kinetics Enzyme kinetics deals with the rate of enzyme reaction and how it is affected by various chemical and physical conditions. Kinetic studies of enzymatic reactions provide information about the basic mechanism of the enzyme reaction and other parameters that characterize the properties of the enzyme. The rate equations developed from the kinetic studies can be applied in calculating reaction time, yields, and optimum economic condition, which are important in the design of an effective bioreactor.

In order to understand the effectiveness and characteristics of an enzyme reaction, it is important to know how the reaction rate is influenced by reaction conditions such as substrate, product, and enzyme concentrations.

If we measure the initial reaction rate at different levels of substrate and enzyme concentrations, we obtain a series of curves like the one shown in Figure 2.

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From these curves we can conclude the following: The reaction rate is proportional to the substrate concentration that is, first-order reaction when the substrate concentration is in the low range. The reaction rate does not depend on the substrate concentration when the substrate concentration is high, since the reaction rate changes gradually from first order to zero order as the substrate concentration is increased.

The maximum reaction rate rmax is proportional to the enzyme concentration within the range of the enzyme tested. The rate is proportional to CS first order for low values of CS, but with higher values of CS, the rate becomes constant zero order and equal to rmax. Since Eq. Brown proposed that an enzyme forms a complex with its substrate.

The complex then breaks down to the products and regenerates the free enzyme. The main concept of this hypothesis is that there is a topographical, structural compatibility between an enzyme and a substrate which optimally favors the recognition of the substrate as shown in Figure 2. The reaction rate equation can be derived from the preceding mechanism based on the following assumptions: Enzyme Kinetics 1.

The amount of an enzyme is very small compared to the amount of substrate. The product concentration is so low that product inhibition may be considered negligible. In addition to the preceding assumptions, there are three different approaches to derive the rate equation: Michaelis-Menten approach Michaelis and Menten, It is assumed that the product-releasing step, Eq. This is an assumption which is often employed in heterogeneous catalytic reactions in chemical kinetics. Therefore, enzymes can be analogous to solid catalysts in chemical reactions.

Furthermore, the first step for an enzyme reaction also involves the formation of an enzyme-substrate complex, which is based on a very weak interaction. Therefore, it is reasonable to assume that the enzyme-substrate complex formation step is much faster than the product releasing step which involves chemical changes. Briggs-Haldane approach Briggs and Haldane, This is also known as the pseudosteady-state or quasi-steady-state assumption in chemical kinetics and is often used in developing rate expressions in homogeneous catalytic reactions.

Practically, it is also our best interests to use as little enzymes as possible because of their costs. Since the first step involves only weak physical or chemical interaction, its speed is much quicker than that of the second step, which requires complicated chemical interaction. This phenomena is fairly analogous to enzyme reactions. Numerical solution: Solution of the simultaneous differential equations developed from Eqs.

Michaelis-Menten Approach If the slower reaction, Eq. The concentration of the enzyme-substrate complex CES in Eq. Since the rate of reaction is determined by the second slower reaction, Eq. Enzyme Kinetics the initial enzyme concentration. By substituting Eq. KM in Eq. Therefore, the value of KM is equal to the substrate concentration when the reaction rate is half of the maximum rate rmax see Figure 2.

KM is an important kinetic parameter because it characterizes the interaction of an enzyme with a given substrate. Another kinetic parameter in Eq. The main reason for combining two constants k3 and CE0 into one lumped parameter rmax is due to the difficulty of expressing the enzyme concentration in molar unit. To express the enzyme concentration in molar unit, we need to know the molecular weight of enzyme and the exact amount of pure enzyme added, both of which are very difficult to determine.

Since we often use enzymes which are not in pure form, the actual amount of enzyme is not known.

Enzyme concentration may be expressed in mass unit instead of molar unit. However, the amount of enzyme is not well quantified in mass unit because actual contents of an enzyme can differ widely depending on its purity. Therefore, it is common to express enzyme concentration as an arbitrarily defined unit based on its catalytic ability.

Care should be taken for the consistency of unit when enzyme concentration is not expressed in molar unit. Briggs-Haldane Approach Again, from the mechanism described by Eqs. This is true with many enzyme reactions.

Since the formation of the complex involves only weak interactions, it is likely that the rate of dissociation of the complex will be rapid. The breakdown of the complex to yield products will involve the making and breaking of chemical bonds, which is much slower than the enzyme-substrate complex dissociation step. Explain when the rate equation derived by the Briggs-Haldane approach can be simplified to that derived by the MichaelisMenten approach.

Then, dCES 2. Therefore, in Eq. Numerical Solution From the mechanism described by Eqs. Since the analytical solution of the preceding simultaneous differential equations are not possible, we need to solve them numerically by using a computer. Among many software packages that solve simultaneous differential equations, Advanced Continuous Simulation Language ACSL, is very powerful and easy to use.

For example, Eq. You can also use Mathematica Wolfram Research, Inc. It should be noted that this solution procedure requires the knowledge of elementary rate constants, k1, k2, and k3. The elementary rate constants can be measured by the experimental techniques such as pre-steady-state kinetics and relaxation methods Bailey and Ollis, pp.

Furthermore, the initial molar concentration of an enzyme should be known, which is also difficult to measure as explained earlier. However, a numerical Enzyme Kinetics solution with the elementary rate constants can provide a more precise picture of what is occurring during the enzyme reaction, as illustrated in the following example problem.

The initial substrate and enzyme concentrations are 0. The values of the reaction constants are: Table 2. To determine how the concentrations of the substrate, product, and enzyme-substrate complex are changing with time, we can solve Eqs. Each block when present must be terminated with an END statement.

The Adams-Moulton and Gear's Stiff are both variable-step, variable-order integration routines. For the detailed description of these algorithms, please refer to numerical analysis textbooks, such Enzyme Kinetics interval integration step size is equal to the comunication interval CINT divided by the number of steps NSTP. The run-time control program is shown in Table 2.

Figure 2. Evaluation of Kinetic Parameters In order to estimate the values of the kinetic parameters, we need to make a series of batch runs with different levels of substrate concentration.

Then the initial reaction rate can be calculated as a function of initial substrate concentrations. The results can be plotted graphically so that the validity of the kinetic model can be tested and the values of the kinetic parameters can be estimated. The most straightforward way is to plot r against CS as shown in Figure 2.

However, this is an unsatisfactory plot in estimating rmax and KM because it is difficult to estimate asymptotes accurately and also difficult to test the validity of the kinetic model.

Therefore, the Michaelis-Menten equation is usually rearranged so that the results can be plotted as a straight line. Some of the better known methods are presented here. The Michaelis-Menten equation, Eq. This can be achieved in three ways: The intercept will be K M rmax , as shown in Figure 2. This plot is known as Lineweaver-Burk plot Lineweaver and Burk, This plot is known as the Eadie-Hofstee plot Eadie, ; Hofstee, The Lineweaver-Burk plot is more often employed than the other two plots because it shows the relationship between the independent variable CS and the dependent variable r.

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This is illustrated in Figure 2. The points on the line in the figure represent seven equally spaced substrate concentrations. The space between the points in Figure 2. On the other hand, the Eadie-Hofstee plot gives slightly better weighting of the data than the Lineweaver-Burk plot see Figure 2. A disadvantage of this plot is that the rate of reaction r appears in both coordinates while it is usually regarded as a dependent variable. The values of kinetic parameters can be estimated by drawing a least-squares line roughly after plotting the data in a suitable format.

The linear regression can be also carried out accurately by using a calculator with statistical functions, spreadsheet programs such as Excel Microsoft. However, it is important to examine the plot visually to ensure the validity of the parameters values obtained when these numerical techniques are used. The advantages of this technique are that: In conclusion, the values of the Michaelis-Menten kinetic parameters, rmax and KM, can be estimated, as follows: Make a series of batch runs with different levels of substrate concentration at a constant initial enzyme concentration and measure the change of product or substrate concentration with respect to time.

Estimate the initial rate of reaction from the CS or CP versus time curves for different initial substrate concentrations.

Estimate the kinetic parameters by plotting one of the three plots explained in this section or a nonlinear regression technique.

It is important to examine the data points so that you may not include the points which deviate systematically from the kinetic model as illustrated in the following problem.

Evaluate the Michaelis-Menten kinetic parameters by employing the Langmuir plot, the Lineweaver-Burk plot, the Eadie-Hofstee plot, and nonlinear regression technique. In evaluating the kinetic parameters, do not include data points which deviate systematically from the MichaelisMenten model and explain the reason for the deviation.

Compare the predictions from each method by plotting r versus CS curves with the data points, and discuss the strengths and weaknesses of each method. Repeat part a by using all data. Examination of the data reveals that as the substrate concentration increased up to 10mM, the rate increased. However, the further increases in the substrate concentration to 15mM decreased the initial reaction rate.

This behavior may be due to substrate or product inhibition. The two data points which were not included for the linear regression were noted as closed circles. You can choose one of the four iterative methods: The Gauss-Newton iterative methods regress the residuals onto the partial derivatives of the model with respect to the parameters until the iterations converge.

You also have to specify the model and starting values of the parameters to be estimated. It is optional to provide the partial derivatives of the model with respect to each parameter. However, the rate predicted from the Lineweaver-Burk plot fits the data accurately when the substrate concentration is the lowest and deviates as the concentration increases. This is because the Lineweaver-Burk plot gives undue weight for the low substrate concentration as shown in Figure 2.

The rate predicted from the Eadie-Hofstee plot shows the similar tendency as that from the Lineweaver-Burk plot, but in a lesser degree.

The rates predicted from the Langmuir plot and nonlinear regression technique are almost the same which give the best line fit because of the even weighting of the data. Enzyme Kinetics 80 8 0. In that case, all data points have to be included in the parameter estimation. By adding two data points for the high substrate concentration, the parameter values changes significantly. In the case of the Langmuir plot, the change of the parameter estimation was so large that the KM value is even negative, indicating that the Michaelis-Menten model cannot be employed.

The nonlinear regression techniques are the best way to estimate the parameter values in both cases. Enzyme Reactor with Simple Kinetics A bioreactor is a device within which biochemical transformations are caused by the action of enzymes or living cells. The bioreactor is frequently called a fermenter6 whether the transformation is carried out by living cells or in vivo7 cellular components that is, enzymes.

However, in this text, we call the bioreactor employing enzymes an enzyme reactor to distinguish it from the bioreactor which employs living cells, the fermenter. A batch enzyme reactor is normally equipped with an agitator to mix the reactant, and the pH of the reactant is maintained by employing either a buffer solution or a pH controller. An ideal batch reactor is assumed to be well mixed so that the contents are uniform in composition at all times.

Therefore, the fermenter was also limited to a vessel in which anaerobic fermentations are being carried out. However, modern industrial fermentation has a different meaning, which includes both aerobic and anaerobic large-scale culture of organisms, so the meaning of fermenter was changed accordingly.

This equation shows how CS is changing with respect to time. With known values of rmax and KM, the change of CS with time in a batch reactor can be predicted from this equation. In a plug-flow enzyme reactor or tubular-flow enzyme reactor , the substrate enters one end of a cylindrical tube which is packed with immobilized enzyme and the product stream leaves at the other end.

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The long tube and lack of stirring device prevents complete mixing of the fluid in the tube. Therefore, the properties of the flowing stream will vary in both longitudinal and radial directions. Since the variation in the radial direction is small compared to that in the longitudinal direction, it is called a plug-flow reactor. If a plug-flow reactor is operated at steady state, the properties will be constant with respect to time. The ideal plug-flow enzyme reactor can approximate the long tube, packed-bed, and hollow fiber, or multistaged reactor.

However, the time t in Eq. Rearranging Eq. V, CS F CS Figure 2. Continuous Stirred-Tank Reactor A continuous stirred-tank reactor CSTR is an ideal reactor which is based on the assumption that the reactor contents are well mixed. Therefore, the concentrations of the various components of the outlet stream are assumed to be the same as the concentrations of these components in the reactor. Continuous operation of the enzyme reactor can increase the productivity of the reactor significantly by eliminating the downtime.

It is also easy to automate in order to reduce labor costs. As can be seen in Eq. For the steady-state CSTR, the substrate concentration of the reactor should be constant. If the MichaelisMenten equation can be used for the rate of substrate consumption rS , Eq. Another approach is to use the Langmuir plot CS r vs CS after calculating the reaction rate at different flow rates. The reaction rate can be calculated from the relationship: However, the initial rate approach described in Section 2.

Inhibition of Enzyme Reactions A modulator or effector is a substance which can combine with enzymes to alter their catalytic activities. An inhibitor is a modulator which decreases enzyme activity. It can decrease the rate of reaction either competitively, noncompetitively, or partially competitively. Competitive Inhibition Since a competitive inhibitor has a strong structural resemblance to the substrate, both the inhibitor and substrate compete for the active site of an enzyme.

The formation of an enzyme-inhibitor complex reduces the amount of enzyme available for interaction with the substrate and, as a result, the rate of reaction decreases. A competitive inhibitor normally combines reversibly with enzyme. Therefore, the effect of the inhibitor can be minimized by increasing the substrate concentration, unless the substrate concentration is greater than the concentration at which the substrate itself inhibits the reaction.

The mechanism of competitive inhibition can be expressed as follows: In this book, both terminologies are used. It is interesting to note that the maximum reaction rate is not affected by the presence of a competitive inhibitor. However, a larger amount of substrate is required to reach the maximum rate. The graphical consequences of competitive inhibition are shown in Figure 2. Noncompetitive Inhibition Noncompetitive inhibitors interact with enzymes in many different ways.

They can bind to the enzymes reversibly or irreversibly at the active site or at some other region. In any case the resultant complex is inactive. The mechanism of noncompetitive inhibition can be expressed as follows: The graphical consequences of noncompetitive inhibition are shown in Figure 2. Note that making these plots enables us to distinguish between competitive and noncompetitive inhibition. Several variations of the mechanism for noncompetitive inhibition are possible.

One case is when the enzyme-inhibitor-substrate complex can be decomposed to produce a product and the enzyme-inhibitor complex. This mechanism can be described by adding the following slow reaction to Eq. The derivation of the rate equation is left as an exercise problem. Other Influences on Enzyme Activity The rate of an enzyme reaction is influenced by various chemical and physical conditions.

Some of the important factors are the concentration of various components substrate, product, enzyme, cofactor, and so on , pH, temperature, and shear. The effect of the various concentrations has been discussed earlier. In this section, the effect of pH, temperature, and shear are discussed. The optimum pH is different for each enzyme.

For example, pepsin from the stomach has an optimum pH between 2 and 3. Chymotrypsin, from the pancreas, has an optimum pH in the mildly alkaline region between 7 and 8. The reason that the rate of enzyme reaction is influenced by pH can be explained as follows: Enzyme is a protein which consists of amino acid residues that is, amino acids minus water. The amino acid residues possess basic, neutral, or acid side groups which can be positively or negatively charged at any given pH.

As an example Wiseman and Gould, , let's consider one acidic amino acid, glutamic acid, which is acidic in the lower pH range. On the other hand, an amino acid, lysine, is basic in the range of higher pH value.

An enzyme is catalytically active when the amino acid residues at the active site each possess a particular charge. Therefore, the fraction of the catalytically active enzyme depends on the pH. Let's suppose that one residue of each of these two amino acids, glutamic acid and lysine, is present at the active site of an enzyme molecule and that, for example, the charged form of both amino acids must be present if that enzyme molecule is to function. Effect of Temperature The rate of a chemical reaction depends on the temperature according to Arrhenius equation as 2.

The temperature dependence of many enzyme-catalyzed reactions can be described by the Arrhenius equation. An increase in the temperature increases the rate of reaction, since the atoms in the enzyme molecule have greater energies and a greater tendency to move. However, the temperature is limited to the usual biological range. As the temperature rises, denaturation processes progressively destroy the activity of enzyme molecules.

This is due to the unfolding of the protein chain after the breakage of weak for example, hydrogen bonds, so that the overall reaction velocity drops. Some enzymes are very resistant to denaturation by high temperature, especially the enzymes isolated from thermophilic organisms found in certain hot environments. Effect of Shear Enzymes had been believed to be susceptible to mechanical force, which disturbs the elaborate shape of an enzyme molecule to such a degree that denaturation occurs.

The mechanical force that an enzyme solution normally encounters is fluid shear, generated either by flowing fluid, the shaking of a vessel, or stirring with an agitator. The effect of shear on the stability of an enzyme is important for the consideration of enzyme reactor design, because the contents of the reactor need to be agitated or shook in order to minimize mass-transfer resistance. However, conflicting results have been reported concerning the effect of shear on the activity of enzymes.

Charm and Wong showed that the enzymes catalase, rennet, and carboxypeptidase were partially inactivated when subjected to shear in a coaxial cylinder viscometer. The remaining activity could be correlated with a dimensionless group gammatheta, where gamma and theta are the shear rate and the time of exposure to shear, Enzyme Kinetics respectively.

However, Thomas and Dunnill studied the effect of shear on catalase and urease activities by using a coaxial cylindrical viscometer that was sealed to prevent any air-liquid contact.

They found that there was no significant loss of enzyme activity due to shear force alone at shear rates up to sec They reasoned that the deactivation observed by Charm and Wong was the result of a combination of shear, air-liquid interface, and some other effects which are not fully understood.

Charm and Wong did not seal their shear apparatus. This was further confirmed, as cellulase deactivation due to the interfacial effect combined with the shear effect was found to be far more severe and extensive than that due to the shear effect alone Jones and Lee, Enzyme Kinetics Objectives: The objectives of this experiment are: To give students an experience with enzyme reactions and assay procedures 2.

To determine the Michaelis-Menten kinetic parameters based on initial-rate reactions in a series of batch runs 3. To simulate batch and continuous runs based on the kinetic parameters obtained Materials: Spectrophotometer 2. Glucose assay kit No. Cellobiose 5. Water bath to control the temperature of the jacketed vessel Calibration Curve for Glucose Assay:

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