7.014 Section: Enzyme KineticsFor an enzyme catalyzed reaction whereenzyme + substrate -----------> productthe kinetic property of an enzyme is determined by a series of experiments. In theseexperiments, the initial rate of product formed (in mmoles/min) is measured for a fixedconcentration of enzyme as the concentration of substrate is varied. Shown below are theresults of several such measurements for a particular enzyme at a particular concentration:01020304050Kinetics dataVelocity[substrate (mM)]a) What does each data point represent?b) What is meant by initial velocity?c) Why does the curve plateau above 20 mM?d) Estimate Vmax & Km for this enzyme.Solutions to Enzyme Kinetics01020304050Kinetics dataVelocity[substrate (mM)]a) What does each data point represent?Each data point represents the initial rate of product formation at that particular substrateconcentration.b) What is meant by initial velocity?The rate of product formation at a very early point in the reaction. At this time, there is very littleproduct yet formed, and the reaction is virtually one directional. With time, each experiment will reachan equilibrium where the net product formed = 0.c) Why does the curve plateau above 20 mM?At concentrations of substrate below 20 mM, some of the enzyme remains free. When additionalsubstrate is added, more of the enzyme is complexed with substrate and therefore more product isproduced per minute. Above 20 mM of substrate, the enzyme is nearly completely complexed withsubstrate, so additional substrate does not increase the rate.d) Estimate Vmax & Km for this enzyme.Vmax = 50 mmoles/minuteKm = 2.5
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