The enzymic degradation of laminarin. 2. The multicomponent nature of fungal laminarinases

Abstract

The degradation of laminarin by fungi is achieved by a family of closely related enzymes. These enzymes were fractionated by adsorption and paper chromatography and have been found to comprise an exo-[beta]-D-(l[forward arrow]3)-glucanase, 1 or more endo-[beta]-D-(1[forward arrow]3)-glucanases and a [beta]-glucosidase of low specificity. Individual enzymes have been obtained in a relatively pure state by refractionation on calcium hydroxyapatite and their action on insoluble laminarin and lamin-aridextrins was studied and compared with the action of the un-fractionated complex. Fungi almost invariably possessed both exo-and endo-[beta]-D-(l[forward arrow]3)-gluconases; the sole exception was the laminarinase prepared from Penicillium stipitatum, which lacked an exohydrolytic component. A spectrum of laminarinase types has been recognized, ranging from those having predominantly exohydrolytic activity to those with a predominantly endohydrolytic action on laminarin. An examination of the laminarinase of Myrothecium verrucaria IMI25291 suggested that the individual enzyme components exerted a synergistic effect on each other and a scheme of laminarin hydrolysis is presented. In a few laminarin hydrolysates D-mannose was repeatedly detected but chemical analysis of the laminarin used failed to reveal its presence. Mannitol and[beta]-(1[forward arrow]6)-linked glucosides have also been observed during laminarin degradation and the tentative identification of 3,6-di-O-[beta]-glucosyl-D-glucose in such hydrolysates suggested that [beta]-(l[forward arrow]6) -linked branch points occur in the laminarin molecule.