Calculating the turnover number
A reaction contains 0.01 μmol of enzyme and has a Vmax of 2 μmol of product per minute. What is kcat?
Answer B: explanation for every choice
A
This inverts the ratio, dividing enzyme by Vmax.
B
Correct. kcat = Vmax/[E]total = 2/0.01 = 200 min⁻¹, and 200 ÷ 60 ≈ 3.3 s⁻¹.
C
200 is the value per minute. It wasn't converted to seconds.
D
This multiplies by 60 instead of dividing.
Takeawaykcat = Vmax/[E]total. Watch the time units.
Equation usedTurnover number and catalytic efficiency
Next question →Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb154.