CONICET | Buscador de Institutos y Recursos Humanos

The kcat /KM ratio, where kcat is the catalytic constant for the conversion of substrateinto product, and KM is the Michaelis constant, has been widely used as a measureof enzyme performance, but recent analyses have underscored the inadequacy ofthis ratio to describe the efficiency of a biocatalyst, particularly when employed asa criterion for selecting between enzyme variants for industrial purposes. The mainproblem with this kinetic relationship is that it neglects the contribution of importantfactors operating in actual bioprocess conditions, such as substrate concentrationsand product inhibition, leading to unreal expectations on enzyme performance anderroneous selection of the most adequate biocatalyst. Two complementary formalisms,the efficiency function and the catalytic effectiveness, have been introduced toincorporate important features of any bio-industrial system. We review herein therationales underlying each derivation, and the strengths and fields of application ofboth strategies. Examples of different situations, including continuous and batch-typereactors, as well as reversible and irreversible processes, are provided, together withrecommendations on the use of both approaches.