Michaelis-Menten Equation
Relates reaction velocity to substrate concentration
Formula
v = (Vmax [S]) / (Km + [S])
- v = initial reaction velocity
- Vmax = maximal velocity
- [S] = substrate concentration
- Km = substrate concentration at v = Vmax/2
Lineweaver-Burk (linear)
1/v = (Km/Vmax)(1/[S]) + 1/Vmax
Slope = Km/Vmax; intercept = 1/Vmax
Example
Given: Vmax = 120 µM/min, Km = 30 µM, [S] = 60 µM.
v = (120 × 60) / (30 + 60) = 7200 / 90 = 80 µM/min.
Answer: v = 80 µM/min
Common Mistakes
Units mismatch
Keep consistent units for Vmax, [S], and v.
Km interpretation
Km is not always an affinity constant; conditions matter.
FAQ
Does inhibition change the equation?
Competitive/noncompetitive inhibitors alter apparent Km or Vmax; use modified forms accordingly.
Can I estimate Km from v vs [S]?
Yes; fit data to the hyperbolic equation or use linear transforms.