Summary: Z theo~ BioL (1985) 113, 711-717
A Diffusion Michaelis--Menten Mechanism: Continuous
Conformational Change in Enzymatic Kinetics
Department of Physical Chemistry, The Hebrew University of
Jerusalem, Jerusalem 91904, Israel
(Received 17 April 1984, and in final form 31 October 1984)
We present a simple model which extends the Michaelis-Menten mechan-
ism by incorporating a continuous protein conformational change in enzy-
matic catalysis. This model can represent a quantitative version for "rack"
or "induced fit" mechanisms. In the steady-state it leads to an equation
of the Michaelis-Menten form, but with the catalytic step at the active site
showing strong dependence on solvent viscosity. We suggest that a careful
examination of solvent viscosity effects on enzymatic activity may serve as
a test for the conformational change hypothesis.
"How do enzymes work?" is a central question in biochemical kinetics.
The classical theories of enzyme action (Haldane, 1930; Laidler & Bunting,
1973) assume that two central steps are involved: the binding of the substrate
to a specific site in the enzyme and the chemical reaction that occurs at this