A kinetic theory of enzymatic oxidation-reduction reactions based on a postulate of electron conduction in a macromolecular enzyme with an application to active transport of small ions across biological membranes

Abstract

Experimental evidence of electron conduction within a protein has recently been given by Rosenberg. This paper gives a quantitative kinetic treatment of a hypothetical enzyme reaction that is rate-limited by electron conduction within the enzyme molecule. In particular, a kinetic theory of enzymatic oxidation-reduction has been built considering the enzyme to consist of a large protein molecule catalyzing oxidation-reduction of two different substrates at two different enzymatic sites on the same macromolecule. The electrons on each substrate are assumed in free and rapid equilibrium with the substrate's enzymatic site on the protein molecule. The rate-limiting process is assumed to be electron conduction in the protein molecule between the two sites. The resulting substrate concentrationvs. time curves appear to be zero order in some cases, and appear first order in other cases within narrow substrate concentration limits. Quantitative criteria are given for testing whether experimental data fit this type of kinetics. Oxidation-reduction reactions by this mechanism seem likely to be coupled to countercurrents of small charged ions in the surrounding solution, which suggests that a similar process could produce active transport of small ions across biological membranes.