The enzymic degradation of laminarin. 3. Some effects of temperature pH and various chemical reagents on fungal laminarinases

Abstract

An attempt is made to correlate the data with the multicomponent nature of the enzyme systems. The exo- and endo-[beta]-D-(l[forward arrow]3)-glucanases investigated showed different temperature optima under the conditions of assay. Generally endohydrolytic enzymes appeared to be more thermostable than exo-enzymes, though certain endohydrolytic enzymes had a low temperature optimum. Exo-[beta]-D-(l[forward arrow]3)-glucanases exhibited optimum activity at pH 4.9-5.0, whereas endo-enzymes were most active at pH 6.0. Fungal [beta]-D-(l[forward arrow]3)-glucanases were not specifically ion-activated enzymes, though several metal ions enhanced activity; the decreasing order of catalytic efficiency was Fe3+, Mn2+, CO2+, Zn2+ ions. Exo-[beta]-D-(l[forward arrow]3)-glucanases were preferentially inhibited by thiol reagents but could be protected or reactivated by reduced glutathione. Laminarin hydrolysis was also curtailed by the action of glucono-(1[forward arrow]4)-lactone; this was chiefly a result of specific inactivation of [beta] -glucosidase components.