AN ANALYSIS OF THE KINETICS OF ENZYMATIC SYSTEMS WITH UNSTABLE SPECIES

We present a general kinetic analysis of the Michaelis-Menten mechanis m for the case in which the substrate, the enzyme-substrate complex, a nd the product are unstable. The equations for the rapid equilibrium c onditions are obtained as a particular case of the general equations o f the transient-phase. The kinetic data analysis which we suggest is b ased on the time progress curve of the product of the enzymatic reacti on, or on the progress curve of the species into which the immediate p roduct is transformed. This analysis allows the determination of the r ate and equilibrium constants if adequate experimental results are ava ilable. It assumes, in contrast to most previous treatments of enzyme kinetics, that the concentration of the enzyme is much higher than tha t of the substrate. Since this condition often is satisfied inside cel ls, it can be more relevant to physiological problems than the classic al assumption, [E] << [S], which sooner pertains to the situation in t he laboratory.