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

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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.