A kinetic analysis of coupled sequential enzyme reactions

30 April 2018, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


As a case study, we consider a coupled enzyme assay of sequential enzyme reactions obeying the Michaelis--Menten reaction mechanism. The sequential reaction consists of a single-substrate, single-enzyme non-observable reaction followed by another single-substrate, single-enzyme observable reaction (indicator reaction). In this assay, the product of the non-observable reaction becomes the substrate of the indicator reaction. A mathematical analysis of the reaction kinetics is performed, and it is found that after an initial fast transient, the sequential reaction is described by a pair of interacting Michaelis--Menten equations. Timescales that approximate the respective lengths of the indicator and non-observable reactions, as well as conditions for the validity of the Michaelis--Menten equations are derived. The theory can be extended to deal with more complex sequences of enzyme catalyzed reactions.


Coupled enzyme assay
Sequential enzymes
slow manifolds
timescale separation
singular perturbation analysis
initial rate experiments
reactant stationary approximation
Schnell-Mendoza equation
Biological Sciences


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