A Comparison of Protease Active Sites and their Ability to Process Silicon-Based Substrates

Abstract

Many enzymes have been identified that can participate in the hydrolysis of alkoxysilanes; each with a different degree of specificity. Our working hypothesis was that the nature of the active site of the enzyme (i.e., the compatibility of binding pockets with the substrate) could have a direct effect on the rate of catalysis. This communication reports our experiments on the relative rates of hydrolysis of a model alkoxysilane, phenyltrimethoxysilane (PTMS), by three proteases: trypsin, α-chymotrypsin, and pepsin. Trypsin which typically accepts amino acids bearing positively charged basic residues was not particularly proficient for the hydrolysis of PTMS. On the other hand, both α-chymotrypsin and pepsin, each of which contains a binding pocket, or two in the case of pepsin, suitable for accommodating aromatic residues, were more suitable for mediating hydrolysis. This report provides some preliminary data to support the hypothesis that the architecture of the enzyme active site is important in determining the proficiency with which an enzyme will process a given organosilicon substrate.