Rational polynomial equation helps to select among homeomorphic kinetic models for cholinesterase reaction mechanism

Abstract

The hydrolysis of substrates by cholinesterases does not follow the Michaelis-Menten reaction mechanism. In addition to the inhibition by excess substrate, these enzymes often show an unexpectedly high activity at low substrate concentrations. It seems that these deviations are the consequence of an unusual architecture of the active site, buried deep inside the core of the molecule. Kinetic data and structural evidence allow for a detailed prediction of the events during a very fast substrate turnover. Recently, we presented a procedure which provides an unbiased framework for mathematical modelling of the complex cholinesterase reaction [J. Stojan, M. Goličnik, D. Fournier, Rational polynomial equation as an unbiased approach for the kinetic studies of Drosophila melanogaster acetylcholinesterase reaction mechanism, Biochim. Biophys. Acta 1703 (2004) 53–61]. It is based on regression analysis of a rational polynomial using classical initial rate data. Here, we extend the use of the rational polynomial rate equation for finding and comparing some selected homeomorphic reaction schemes useful for the mechanistic interpretation of cholinesterase kinetic data.