Properties of Enzyme Catalysts

Properties of Enzyme CatalystsIntroductionEnzymesEnzymes be single or ninefold -chain proteins that act as a biological throttles with the ability to promote specific chemical rxn under the delicate antecedent that prevail in most living organism.Over-view of Enzymes particle acceleratorsAll reception in the body ar mediated by enzymes, which atomic number 18 protein catalysis that increase the reckon of chemical answerion without being changed in boilersuit process. Among the many biologic re swear out that ar energetic possible, Enzyme selectively channel reactant c e realed substratum into useful pathways. Enzynes so direct all metabolic events.Enzyme be Protein Catalyst that increase the velocity of the chemical rxn, and be non consumed during the rxn they catalyse. Some type of RNA act like a Enzyme, RNA with catalytic activity are called Ribozymes. Enzymes are protein catalysts, they influence the dynamics scarce not the thermodynamics of a reactionIncrease t he wander of a chemical reactionDo not alter the equilibriumProperties of enzymesEnzyme blood corpuscles contain a special sackful called a active post. The active point contain amino sultry side chain that bring about a three dimention surface complementary to the subst evaluate . the active site bind the substratum , var.ing an enzyme subst locate (ES) complex. The ES is converted to enzyme crossroad(EP), which subsequently dissociated to enzyme and product.catalytic efficiency Most enzyme catalytic rxn are superiorly consequenceive , proceeding from 103 to 108 eras high-velocity than the uncatalysed rxn. Eacg enzyme molecule is capable of transforming 100 to 1000 substrate molecules into product to each bingle sec. The number of molecules of substrate converted to product is called the turnover no.Characterstic of EnzymesCertain import is miserable pith have unique capacity of speedingup chemical rxn without being alter after the rxn, they acceleration the veloc ity of the rxn without needed signly it. Substance that behave in this manner are called catalyst or catalytic agent. For eg hydrogen and oxygen do not combine to any appreciable extent under normal atmospheric presumption. However unlike platinum , while is in perfect , enzyme are essential compound produce by living organism. Thus we whitethorn define enzyme as organic catalyst produced by a organic cell.The three distinctive characterstic are 1)specificity. 2)high Catalyst rate 3)high capacity for regulation.A general model of reaction kinetics of biological sy stalksDyanamic numeric model in biotechnology require beside the information require the stoiciometry ok the biological rxn system.. The identification of a priori unknown reaction kinetics is often a critical projection due to the non- transmission channelarity and (over-) parameterization of the model comparabilitys introduced to account for all the possible modulation phenomena. The contri simplyion of this pa per is to propose a general formulation of reaction kinetics, as an extension of the Michaelis-Menten kinetics, which al menials limitation/activation and inhibition effects to be described with a reduced number of parameters.The dianamic model of a perfectly stirred tank bioreactor is normally derived from a mass balance which lead to a differential gear eq systwm for the submergence vector) = c0r(c(t))=q(c(t))cx0(t)The matrix Rm*n contains the information on the stoichiometry of the reaction system and is usually timeinvariant. The biological reactions r R m are catalysed by the viable biomass, whose ingress is denoted by cx0(t) and the specific reaction rate vector q Rm is usually a non-linear function of the concentrations. D R is the renewal (or dilution) rate and u R n containsthe reactor input/output conditions. There are a outstanding variety of mathematical descriptions of the reaction kinetics available in the literature. A systematic approach is, thereof, incumbe nt to discover the best model structure and the best values ofthe model parameters with respect to somewhat enforce criterion. For instance, in terms of model identification, the optimal structure is characterised by minimal correlations amid parameters and maximal identifiability properties. In terms of state estimation and control, however, simplicity and (non-)linearity play important roles.5ENZYME CATALYSTMost of the rxn that occur in living organism are catalyst by molecule called enzyme. Most enzymes are proteins (certain RNA molecules likewise act as enzyme).An enzyme is in specific in its action. Many enzymes catalyst only the conversion of a particular reactant to a particular product other enzyme catalyst only a certain line of rxn(by ester hydrolysis) . Enzyme speed up rxn rate very substantionally and in their absent most biological rxn occur . The molecule an enzyme act on is called the substrate.the substrate bind to a specific active site on the enzymeso form as enzyme substrate complex. Some physiological poison act by bind to active site of an enzyme,there auction block the action of the enzyme.the structure of an inhibitor may resemble the structure of enzyme substrate .Cyanide act by blocking the enzyme cytochrome oxidase.The single called Escherichia coli, a bacterium that flourished in human colons, contain about 2500 different enzymes .6Enzyme Kinetics1 Michaelis-Menten Kinetics 2.Lineweaver-Burk Kinetics 3. Hanes-Woolf Kinetics4. Eadie-hofstee 5. Reversible Inhibition7K1 k2E+S ES E+Pk-1 k-2E is the free enzyme , S is the substrate, ES is the enzyme substrate complex p is the product. Thp overall rxn is s gives p. The enzyme is fancied in step 1 and rearranged in step 2.Enzymes mickle catalyze up to some(prenominal) million reactions per endorse 2.Enzyme rates depend on solution conditions and substrate concentration. Conditions that denature the protein abolish enzyme activity, such as high temperatures, extremes of pH or high salt concentrations, while raising substrate concentration tends to increase activity. To find the upper limit speed of an enzymatic reaction, the substrate concentration is increased until a constant rate of product formation is seen. This is shown in the saturation curve on the right. Saturation happens because, as substrate concentration increases, more than and more of the free enzyme is converted into the substrate-bound ES form. At the maximum velocity (Vmax) of the enzyme, all the enzyme active sites are bound to substrate, and the amount of ES complex is the same as the total amount of enzyme. However, Vmax is only nonpareil kinetic constant of enzymes. The amount of substrate needed to achieve a given rate of reaction is also important. This is given by the Michaelis-Menten constant (Km), which is the substrate concentration required for an enzyme to reach genius-half its maximum velocity. Each enzyme has a feature article Km for a given substrate, and this contr ibute show how tight the binding of the substrate is to the enzymeIn most experimental studies on enzymes kinetics, the enzyme concentrationis much less than the substrate concentration EES-EP0=(E -ES)(kES-P)-(+)ESIf is the initial enzyme concentration than E=E+ES.since the conc is Eduring the rxn is generally not known while E is known , we replace E by EThe const rate is =-R=ES-ESR=ES-(S+ESSince the concentration of the intermediate ES is very small, we haveUsually,the rxn is followed only to a fewer percent completion and the initial rate determined. Setting the product concentration Pequal to 0 and Sequal to SWe get as the initial rate rwhere the Michaelis Menten const is defined by . The reciprocal of above eq is1/r= 1/Equation 2 is the Michaelis Menten eq , and above eq is the Lineweaver Burk eq. One measure r for several S values with E held fixed. The constantSince E is known . strictly speaking r is not the rate at t=0 , since there is a short induction period before stea dy state condition are establish .Although many exp studies on enzyme kinetic give a rate law in agreement with the Michaelis Menten eq .the mech a is grossly over simplified. For one thing , there is much establish that , while the substrate is bound to the enzyme , it generally undergoes a chemical change before being released as product . hence a better model isE + S ES EP E+ PThe above model gives a rate law that has the same form as the Michaelis Menten eq but the const are replaced const with diff signifi croupece . Enzyme rxn are quite fast but can be studied development classical methods by keeping E and Svery obtuse.Lineweaver- Burk EquationThe method describe for the determination of is someone complex and therefore simpler method have been devised. Two such method are given downstairsFirst method-a convient instrument of evaluating and is to plot kinetic selective information as the reciprocals of v and (S) where v velocity and (S) is the total conc of substrate. s uch a double reciprocal was proposed by Hans Lineweaver and Dean Burk in 1934. If one take the reciprocal of Michaelis Menten eq, the following eq is formedThis is known as Lineweaver- Burk Equation. This eq is the form y=mx+b, if one condition the inconsistent to b and 1/(s). When one plots a graph against these cardinal variable , a straight line is obtained . the slop of this line twins to and the 1/v end corresponds to 1/. Since can be determine from the intercept , the can be calculated .Second method some other graphical method for the measurement of for experimentel data on V as a measure of (S) makes use of the above Lineweaver- Burk Equation . multiplicationon sides of the by (S) givesA plot of verses (S) gives a straight line on axis is and the slope is and can be obtained from intercepy of the slope. A lineweaver burk plots provide a quick test for adhereance to Michaelis Menten eq kinetic and allows easily evaluation of the critical const . it also allow the discr imination between diff agreeables of enzyme inhibition and regulation. A disadventure of lineweaver-Burk plot is that a dour extrapolation is often require to determine , which corresponds uncertainty in the result. Consequently , other way of plotting the data are sometimes used.Alternate plot are based on Hanes-eq s/vSo that v/s is plan against v. The relative merit of the Lineweaver-Burk, Hanes and Edlie-Hoffstee eq for the determination of and are llustrated under in fig. Using the same touch on of e ixperimental values of v for a series of substrate concentration . it can be seen that the lineweaver-Burk eq gives the unequal diffusion of points and greater emphasis to the points at low substrate concentration that are national to a greater experimental error, whilst the Edlie-Hoffstee eq and a Hans eq gives a better distribution of points. In the face of the Hans plot , greater emphasis is placed on the experimental data at high substrate1)Lineweaver plot 2)Hanes plot 3 ) Eadie-hofstee plotLineweaver burk, Hanes and Eadie hofstee plot the same set of experimental data of the effect of substrate conc. S on the initial rate v of the enzyme catalyst rxn.Reversible InhibitionNow apportion the effect of reversibly-binding inhibitors on an enzyme. If an inhibitor binds reversibly at the same site as the substrate, the inhibition is referred to as competitive. If the inhibitor binds to another site on the enzyme, the binding is described as noncompetitive. These two alternative behaviors may be magisterial by their effects on Lineweaver-Burk or Hanes-Woolf plots. If a reversible inhibitor can bind to the enzyme active site in place of the substrate, it is described as a competitive inhibitor. In pure competitive inhibition, the inhibitor is assumed to bind to the free enzyme but not to the enzyme-substrate (ES) complex. The binding is described as shown belowHere Ki is the dissociation constant for the EI complex. EI does not react to form E + P, and th e enzyme is unable to bind both S and I at the same time. There are several graphical methods for detecting and analyzing competitive inhibition. The Michaelis-Menten, Lineweaver-Burk, and Hanes-Woolf equivalences can all be modified to include a term that describes the inhibition by I. Choose one of the cases below to consider each of these in more detail The Michaelis-Menten compare for competitive inhibition is The Lineweaver-Burk equation for competitive inhibition is The Hanes-Woolf equation for competitive inhibition isNoncompetitive InhibitionIf a reversible inhibitor can bind to the enzyme at a site that is distinct from the active site, it is described as a noncompetitive inhibitor. In pure noncompetitive inhibition, the inhibitor binds with equal affinity to the free enzyme and to the enzyme-substrate (ES) complex. The binding is described as shown belowHere Ki is the dissociation constant for either the EI complex or the IES complex. Neither of these complexes can rea ct to form E + P. There are several graphical methods for detecting and analyzing noncompetitive inhibition. The Michaelis-Menten, Lineweaver-Burk, and Hanes-Woolf equations can all be modified to include a term that describes the inhibition by I. Choose one of the cases below to consider each of these in more detail The Michaelis-Menten equation for noncompetitive inhibition is The Lineweaver-Burk equation for noncompetitive inhibition is The Hanes-Woolf equation for noncompetitive inhibition is Limiting Kinetics of Enzyme-Catalysed ReactionsAt very low concentrations of substrate many enzyme-catalysed reactions display approximately encourage-order kinetics, with rate given by the following equationv = kA E0 A . . . . . . . in which the symbol kA (or, in general, kR for a reactant R) is the apparent second-order rate constant or specificity constant and E0, which may also be written as Et or Estoich, is the total or stoichiometric concentration of catalytic centres. The rati onale for the subscript 0 is that the total enzyme concentration is normally the concentration at the instant of mixing, i.e. at time zero. Conversely, at very high substrate concentrations the same reactions commonly display approximately first-order kinetics (zero-order with respect to substrate) v = k0 E0 . in which k0, which may also be written as kcat is the apparent first-order rate constant. Although these limiting types of behaviour are not universally observed, they are more common than Michaelis-Menten kinetics)and provide a basis for classifying inhibitory and other effects supremely of the need for Michaelis-Menten kinetics.The quantity k0E0 is given the symbol V and the get word limiting rate. It is particularly useful when k0 cannot be calculated because the total catalytic-centre concentration is unknown, as in studies of enzymes of unknown purity, sub-unit structure and molecular mass. The symbol Vmax and the names maximum rate and maximum velocity are also in wide spread use although under normal circumstances there is no exhaustible substrate concentration at which v = V and hence no maximum in the mathematical sense. The form Vmax is convenient in speech as it avoids the need for a cumbersome distinction between capital V and lower case v. When a true maximum does occur the symbol vmax (not Vmax) and the name maximum rate may be used for the true maximum value of v but care should be taken to avoid confusion with the limiting rate.Enzyme MechanismEnzyme kinetic studies, unneurotic with the other typeof investigating have led to inside into the way in which enzyme exert their catalytic action.aspects of this are of special absorb . This specificityof enzymes is explained in terms of the an elaborating of Fischers lock and keywhich is concerned with the way in which an enzyme and the substrate fixed together in forming a Enzyme substrate complex and in undergo subsequent rxn . the second aspect is the very high effectiveness of enzyme in c omparison with other catalyst. the high effectiveness of catalyst almost of all time is associate with a low energy of activation for the rxn. in some cases the effect has been attributed to the fact that the enzyme is performing as a bifunctional catalyst, in tha two catalytic group are presentside by side at the active centre.Transition state When a chemical reaction occurs, the energy content of the reacting molecule or atom increases. This is why most chemical reactions, whether they release heat or absorb heat, happen faster as the temperature is raised. The high-energy state of the reactants is called the transition state. For example, in a bond-breaking reaction, the transition state may be one where the reacting bond, although not completely broken, is vibrating at a frequency high enough that it is equally probably to split apart as to reform. Forming reactants or products results in the loss of energy from the transition state. This principle is shown in Figure 1 , where the increased energy of the transition state is stageed as a agglomerate or barrier on the energy diagram. Catalysts reduce the height of the barrier for achieving the transition state.General Catalytic MechanismCatalysed reaction occur by a wide variety of mechanism.There is however one sample that applies to a no of single substrate rxns catalysted by surfaces,enzymes, acids and bases. It is useful to consider this schmene of rxn first show as to appreciate the similarities that exist between certain rxn that are catalysted by different type od catalyst.The rxn schmeC + S X + YX + W P + ZHere C represent the catalyst and s is the substrate X and Y are intermediate , the first of which undergoes a second rxn with a species W to give final product or products P together with the addition substance Z. This scheme shows only the kinetically significance reactions the substate Y and Z undergo other process that do not have any effect on yhe kinetic behaviour. To simplify the tre atment it is assumed that the second rxn does not in the reverse direction this can b ensured if the product P is removed as outlying(prenominal) as it is formed.In surface catalysis X is an adsoption complex, Y and W are non exitance. The const in this case are first order rate const, while is the second order const. In catalysis by acid and base however Y and W play important role. Thus i c is an acid catalyst, rxn 1 involces the transfer of a proton to S,so that Y is the base conjugate to the acid C. In acid catalyst the intermediate X is the protonated substrete SH+ and a rxn 2 is proton is transferred to a species W. The species W therefore has basic properties and it may b molecule of a solvent and a solute. For eg It may be the species Y formed in 1 step . we will see that the kinetic behaviour depends in an important way on wheather the intermediate X transfers its proton to solvent molecule or to a solute molecule. Conversely in base catalyst Y is the acid conjugate to th e base C.the intermediate X is the substrate Molecule minus a proton., and in rxn 2 it accepts a proton from W.again we have a solvent molecule or a solute molecule.in some situations a rate with which a intermediate X undergoes rxn 2 may be sufficiently slow that the first rxn may b regarded as being at equilibrium.the exact condition for this is WXY.since this case corresponds to Arrhenius archetype of an intermediate in eq with the reactants, such intermediate have being called Arrhenius intermediates.The converse case is that the condition is XYthe concentration of X is small and the steady state treatment may be appliedto it. Intermediate of this kind have been called Vant Hoff intermediates. If neither of this of this extreme condition applies , the kinetic situation is more complicated , and the appropriate differential eq have to be solved. Only the equolibium and steady-state treatments are considered here.Equilibrium sermon Arrhenius intermediatesIn this case the equati on Applies. However , the concentration of C and S do not correspond necessary to yhe initial concentration C and S. Since appreciable amount of C and S have been used to form a intermediate X. These initial concentration may be expressed asC=C + SS= S + XAs long as attention is confined to initial rates. Eq a findThis is quadratic in X and can be solve for X. Yhen the reflexion for rate equal to kXW , can be written down. However it os, more useful to consider two special cases.Case 1 if the initial conc of the substrate is much greayer than that of yhe catalyst, that is, if SC, it follows that S X is very close to S, since X cannot exceed C. Eq b there fore reduces to And thusThe rate of rxn thereforeV=XW=This rate eq correspond toa variation of rate of all type represent .At lower substrate conc , when KSY, the rate become independent of S, as long as the condition SC holds, however the rate varies linear with C.This type of behaviour is characteristic or single-substrate rxn on surfaces and of enzyme rxn.For both of these the species Y and W are nonexistence and eq c becomeThe eq is also eq to the Michaelis Menten eq for enzyme rxn. This eq usually writtenWhere is the Michaelis const , is equal to 1/k in the present treatment.In rrn catalysed by acid and base it will be seen that the rate hang in linear with the substrate concentration this is because of the special type of equilibrium that are rapidly established in the sol.Case 2 on the other hand , if the catalyst is greatly in excess of the substrate, that is CS eq a reduces toAnd the rate of rxn isThe rate now varies linearily with the concentration of substrate , but the variation with the catalyst concentration .(b)The rate of reaction as a function of substrate conc for the case in which SC (a) rate of rxn as a function of catalyst concentration for the caseCSSteady-state TreatmentVan,t hoff intermediateIf the condition W applies, the concentration of X is small and the steady state treatmen t is available. The steady-state issubstitution of C -X for C and of S-X for S givessince X is very small the term in can be neglected with its approximation above eq givesthe rate is thereforethis eq again indicates that at low conc of either catalyst or substrate the rate is proportional to either C or S at a higher concentration of either the rate become independent of that concentration .in catalyst by surface and enzymes , W and Y are nonexistence and the rate eq becomeAn eq of fundamentally this form was first derived by Briggs and Haldane for enzyme reactionCatalyst By EnzymeCatalysis by enzyme , the biological catalyst , is much more specific than that by acids and bases. soe enzyme shows absolute specificity an eg is urease, which only the catalyzed of Urea.A lower degree of specificity is shown by such enzyme as the proteolytic enzymes, which catalyst the hydrolysis of the peptide linkage provided that certain structural condition are contract in the neighbourhood of t he linkage. this is known as group specificity. many enzyme exhibit stereochemical specificity, in that the catalyze the rxn of one stereochemical form and not the other.the proteolytic enzyme.The enzymes are protein but may be associated with non protein substance that essential to the action of enzyme.the action of enzyme shows some resemblance to the catalytic action of acids and bases but is more complicated. the present treatment of enzyme kinetics is confined to the influence concentration, ph, and temperature and to some brief comments about enzymes mechanisms.Measurement of the kinetics of biological systems at towering temperatures utilizing flow techniquesContinuous flow-type reactors have been used to assume the kinetics of biological systems for quite some time. For continual media sterilization, tubular flow reactors are particularly useful being simple in character and belatedly to control. However, one aspect quite often neglected in sterilization calculations is the domicil time distribution of the reactor system. Serious errors in estimating the degree of bacterial destruction can be encountered if the residence time distribution is neglected especially when a high degree of destruction is desired. This paper reports a study made to characterize and use the residence time distribution of a tubular reactor in the interpretation of high-temperature, short exposure time data for inactivation of Bacillus stearothermophilus spores. Mathematical models accounting for the residence time distribution of the tubular reactor have been proposed and employed to obtain high-temperature death-rate data.14ResultSince enzymatic reactions are so important to biological chemical reactions, it is of great interest to be able to model them. By use of the study of chemical kinetics, it is possible derive rate equations for the steps involved in an enzymatic reaction. These rate equations are differential equations and can be used to model theconcentrations of each compound in the system. However, this system of differential equations is hard to determine experimentally because of the difficulty of determining the rate equations into theMichaelis-Menten enzyme equation. Many benefits stem from this transition. One benefit is the fact that it is now easy to determine the constants related to the enzyme equations. However, how do we know the Quasi-Steady-State self-reliance is valid? It seems reasonable from a physical argument. Byuse of dimensional analysis, we can give a more inexorable mathematical argument for the Quasi-Steady-State Assumption. The Michaelis-Menten enzyme equation is very important in the study of cellular systems by allowing a model that can be easily derived through experimentation.SummaryEnzymes are single or triune -chain proteins that act as a biological catalysts with the ability to promote specific chemical rxn under the wacky condition that prevail in most living organism. All reaction in the body are media ted by enzymes, which are protein catalysis that increase the rate of reaction without being changed in overall process .than properties of catalyst in which Enzyme molecules contain a special pocket called a active site. Than the characterstic of enzymes where enzyme are organic compound produce by living organism. Thus we may define enzyme as organic catalyst produced by a organic cell. Then we studied the Enzyme Kinetics where studied the five equation1 Michaelis-Menten Kinetics 2.Lineweaver-Burk Kinetics 3. Hanes-Woolf Kinetics 4. Eadie-hofstee 5. Reversible Inhibition.Than we studied the enzyme mechanism where studied two equations theSteady-state TreatmentVan,t hoff intermediate and the Equilibrium Treatment Arrhenius intermediates.