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Michaelis-Menten Kinetics

How enzymes accelerate reactions: v = VmaxΒ·[S] / (Km + [S])

Biochemistry Enzymology Kinetics Inhibition
Inhibitor:
Vmax = 10 Β΅M/s Km = 5 Β΅M Km(app) = 5 Β΅M Vmax(app) = 10 Β΅M/s kcat/Km = β€”

🧬 Michaelis-Menten Enzyme Kinetics

Enzymes bind substrate S into an active site, forming an enzyme–substrate complex ES, then release product P: E + S β‡Œ ES β†’ E + P

Under steady-state (d[ES]/dt β‰ˆ 0), the reaction velocity follows the hyperbolic Michaelis-Menten equation: v = Vmax Β· [S] / (Km + [S])

Km (Michaelis constant) is the substrate concentration at which v = Vmax/2. A low Km means high affinity. Vmax = kcat Β· [E]total.

Inhibition types:

  • Competitive: Km(app) = Km(1 + [I]/Ki); Vmax unchanged. Inhibitor competes for active site.
  • Uncompetitive: Km(app) = Km/Ξ±'; Vmax(app) = Vmax/Ξ±'. Binds only ES complex.
  • Non-competitive: Km unchanged; Vmax(app) = Vmax/Ξ±'. Binds E and ES equally.

The Lineweaver-Burk double-reciprocal plot (1/v vs 1/[S]) linearises the hyperbola: x-intercept = βˆ’1/Km, y-intercept = 1/Vmax. Each inhibitor pattern shifts the line in a characteristic way.