University13 min

Enzyme kinetics: Michaelis-Menten and Lineweaver-Burk

The Michaelis-Menten equation and what Km and Vmax really mean, the Lineweaver-Burk line read without slips, and the signature of each type of inhibition.

The essentials

1

The mechanism and its assumptions

E+S⇌ES→E+P\ce{E + S <=> ES -> E + P}, constants k1k_1, k−1k_{-1} then kcatk_{cat}. Three assumptions: steady state on the ES complex, d[ES]dt=k1[E][S]−(k−1+kcat)[ES]=0\dfrac{d[\ce{ES}]}{dt} = k_1[\ce{E}][\ce{S}] - (k_{-1} + k_{cat})[\ce{ES}] = 0; conservation of the enzyme, [E]T=[E]+[ES][\ce{E}]_T = [\ce{E}] + [\ce{ES}]; substrate in large excess and initial rates ([S]≈[S]0[\ce{S}] \approx [\ce{S}]_0, no product yet).
2

The Michaelis-Menten equation

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3

Reading the curve

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4

The Lineweaver-Burk line

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5

The two inhibitions to recognise

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