PHYSICAL CHEMISTRY IN BRIEF

CHAP. 9: CHEMICAL KINETICS [CONTENTS] 329

where ES is a complex of the enzyme with the substrate. It is assumed that the concentration of
the enzyme-substrate complex, ES, does not vary with time (steady state principle, see9.5.5),
i.e. that
dcES
dτ

=k 1 cEcS−k 2 cES−k 3 cES= 0.

From this we obtain

cES=

k 1

k 2 +k 3

cEcS.

The kinetic equation of the product formation is

dcP

dτ

=

k 3 k 1

k 2 +k 3

cEcS=

k 3 cE0cS

KM+cS

, (9.174)

wherecE0 =cE+ cES is the initial concentration of the enzyme andKM =

k 3 +k 2

k 1

is the

Michaelis constant.