An examination of the unusual susceptibilities of aminoglycans to enzymatic hydrolysis

Abstract

The hydrolytic susceptibilities of aminoglycans, including chitosan, chitin, water-soluble chitin, chitin azure, and α-(1 → 4)-poly(galactosamine), to a series of commercial enzyme preparation were examined. An unexpectedly large number of enzyme preparations gave rise to varying degrees of aminoglycan hydrolysis. Remarkably, several of these enzyme preparations displayed lytic activities towards chitosan that equaled or surpassed those of established catalysts with chitosanolytic activities, such as chitinase and lysozyme. Thus, based on their dose-response profiles, a number of proteases, such as pepsin, bromelain, ficin, and pancreatin, were more efficient catalysts for chitosan hydrolysis than a commercial chitinase ( Serratia marcescens) and lysozyme preparation. For a cellulase, hemicellulase, lipase, and protease evidence was obtained that strongly suggested the absence of a common lytic agent. Thus, different profiles were observed when the lytic activities of these enzyme preparations were examined in terms of their pH and temperature optima, susceptibilities to substrate concentration and the degree of substrate N-acetylation, and their molecular weight fractions. Similarly, distinctions in hydrolytic efficacy emerged for several enzyme preparations, when chitosan solutions were subjected to two simultaneous or sequential enzyme treatments. Chitosan hydrolysis was also observed upon treatment with human salivary preparations. Preparative-scale hydrolyses of chitosan were performed with papain and hemicellulase preparations at pH 3 and 40°C. The results demonstrate the feasibility of hydrolyzing chitosan, chitin and other aminoglycans with several low-cost enzymes.