MISUSE OF GRAPHICAL ANALYSIS IN NONLINEAR SUGAR-TRANSPORT KINETICS BY EADIE-HOFSTEE PLOTS

It has become common practice to analyse the sugar transport kinetics from initial uptake rates in Saccharomyces cerevisiae cells with Eadie-Hofstee plots. These plots often demonstrate a nonlinear behaviour. They have been resolved incorrectly into two quasilinear components indicating the presence of (at least) two uptake systems or components, with K(m) values differing by a factor of about 10. This graphical analysis neglects the obvious additivity of the two hypothetical systems and is therefore in error. A more efficient way to determine kinetic parameters from initial uptake experiments is to use computer-assisted nonlinear regression analysis.