英文课件-酶2.pptVIP

Enzymes Kinetics Velocity of Reaction For the reaction the rate of reaction is given by rate equation where k is a proportionality constant called the specific rate constant order of reaction: the sum of the exponents in the rate equation Velocity of Enzyme Catalysis consider the reaction whose rate equation is given by the expression the reaction is said to be first order in A, first order in B, and second order overall consider this reaction of glycogen with phosphate Enzyme saturation Initial rate of an enzyme-catalyzed reaction versus substrate concentration Michaelis-Menten Model for an enzyme-catalyzed reaction the rates of formation and breakdown of ES are given by these equations at the steady state Michaelis-Menten Model when the steady state is reached, the concentration of free enzyme is the total less that bound in ES substituting for the concentration of free enzyme and collecting all rate constants in one term gives where KM is called the Michaelis constant Michaelis-Menten Model it is now possible to solve for the concentration of the enzyme-substrate complex, [ES] or alternatively Michaelis-Menten Model in the initial stages, formation of product depends only on the rate of breakdown of ES if substrate concentration is so large that the enzyme is saturated with substrate [ES] = [E]T substituting k2[E]T = Vmax into the top equation gives Michaelis-Menten Model when [S]= KM, the equation reduces to Michaelis-Menten Model it is difficult to determine Vmax experimentally the equation for a hyperbola can be transformed into the equation for a straight line by taking the reciprocal of each side Lineweaver-Burk Plot which has the form y = mx + b, and is the formula for a straight line a plot of 1/V versus 1/[S] will give a straight line with slope of KM/Vmax and y intercept of 1/Vmax such a plot is known as a Lineweaver-Burk double reciprocal plot Lineweaver-Burk Plot KM is the dissociation constant for ES; the gr