Summary MIchaelis-Menten equation - step-by-steo guide

-Central to the
study of enzymes
-Based on the
following concept of enzyme catalysis :




k1 k
E+ S ES > E + P
k2

-
E combines with its substrate to form an encyme substrate

complex ES
ES complex dissociate
can
again to form EtS
,
or can
proceed
to
form E and the
product P
-

The symbols by by
and by a re rate constants

< describe the rates associated with step of the process
each
The concentration
of the
enzyme-substrate complex (ES) , remains
approximately constant until
nearly all the substrate is used.
↳ [ES] maintains a
steady state.


-
The initial
velocity (V) at low substrate concentrations is
directly
proportional to the concentration
of substrate [S]
,
while at
high
substrate concentrations the becomes independent of [S],
velocity
eventually reaching
its maximum value , Umax &




-
The
equation describes the hyperbolic curve obtained when (Vo) is

plotted against [S].
UmaxX[S]
V =




km + [S]
-


Michaelis constant :


k2 + kz
km =



by

km equals (k2 + b) divided
to the rate
of breakdown
of ES
by its
-




rate
of formation (k) .
This means km of an
encyme
indicates the

stability of the ES complex .


However
for many enzymes
:
by is much
greater than ky.
> km becomes
dependent on the relative values
of be and ke , which
a re the rate constants
for ES
formation and dissociation
Under these the km becomes
of the
> circumstances , a measure

degree of affinity of an
enzyme for its substrate


Reciprocal of the Michaelis-Menten equation
-

:




1 km + [S] km 1 1
t

T Vmax[S] Vmax[S] Vmax