Enzyme Kinetics
Part II. Enzyme Inhibition
I. Basic Enzyme Kinetics
For an enzyme obeying the Michaelis-Menten equation:
Figure 1.
Vmax and Km describe the catalytic properties of the enzyme.
The meaning of Km is related to the affinity of the substrate for the enzyme. If Km has a very low concentration - substrate has a high affinity for the enzyme.
Vo = Vmax at very high [S]. Vmax has units same as Vo (mmoles product/min)
Km is [S] when Vo = Vmax/2. Km has units same as [S] (mM)
Vmax is relative to total enzyme used.
Vmax = kcat [E]kcat = catalytic rate constant
kcat is called the turnover number
kcat = substrate moles reacted/mole of enzyme/second
Since [E] is difficult to determine, Vmax/Km is useful.
Vmax/Km measures enzyme efficiency and all enzymes can be compared by using it.
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©Wilbur H. Campbell, 1995; wcampbel@mtu.edu