Cosolvent and pressure effects on enzyme-catalysed hydrolysis reactions

Abstract

Thermodynamics and kinetics of biochemical reactions depend not only on temperature, but also on pressure and on the presence of cosolvents in the reaction medium. Understanding their effects on biochemical processes is a crucial step towards the design and optimization of industrially relevant enzymatic reactions. Such reactions typically do not take place in pure water. Cosolvents might be present as they are either required as stabilizer, as solubilizer, or in their function to overcome thermodynamic or kinetic limitations. Further, a vast number of enzymes has been found to be piezophilic or at least pressure-tolerant, meaning that nature has adapted them to high-pressure conditions. In this manuscript, we review existing data and we additionally present some new data on the combined cosolvent and pressure influence on the kinetics of biochemical reactions. In particular, we focus on cosolvent and pressure effects on Michaelis constants and catalytic constants of α-CT-catalysed peptide hydrolysis reactions. Two different substrates were considered in this work, N-succinyl-L-phenylalanine-p-nitroanilide and H-phenylalanine-p-nitroanilide. Urea, trimethyl-N-amine oxide, and dimethyl sulfoxide have been under investigation as these cosolvents are often applied in technical as well as in demonstrator systems. Pressure effects have been studied from ambient pressure up to 2 kbar. The existing literature data and the new data show that pressure and cosolvents must not be treated as independent effects. Non-additive interactions on a molecular level lead to a partially compensatory effect of cosolvents and pressure on the kinetic parameters of the hydrolysis reactions considered.

Keywords: Catalytic constant; Kinetics; Michaelis constant; TMAO; Urea; α-Chymotrypsin.