Michaelis–Menten velocity at 2K<sub>m</sub>
An enzyme has Km = 2 mM and Vmax = 60 μmol/min. What is the velocity when [S] = 4 mM?
Answer C: explanation for every choice
A
This puts Km in the numerator instead of [S]: (60)(2)/6.
B
30 μmol/min is ½Vmax, the velocity when [S] = Km.
C
Correct. v = (60)(4)/(2 + 4) = 240/6 = 40 μmol/min.
D
Vmax is only approached at saturating substrate concentrations.
Takeawayv = Vmax[S]/(Km + [S]).
Equation usedMichaelis–Menten
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