β-Glucanase of yeast

Abstract

The basal cell wall structure of yeasts which is responsible for the shape and rigidity of the yeast cell is a β-glucan, containing both β 1,3 and β 1,6 linkages (Phaff, 1963). During conjugation, two yeast cells of opposite mating type fuse by dissolution of cell wall material between them, leading to a typical dumbbell-shaped zygote (Conti and Brock, in preparation). Because this morphogenetic process involves new protein synthesis (Brock, 1961), it seems reasonable that enzymes which attack the basal cell wall structure are involved in the conjugation process, and attention has thus been focused on the β-glucanases of yeast. Although extensive work has been done on β-glucanases of filamentous fungi (Reese and Mandels, 1963), mainly in relation to deterioration phenomena, no work has apparently been done on the yeast enzymes. The present paper will show that yeasts contain intracellular β-glucanase activity of a peculiar nature. In addition, this paper will show that yeast β-glucanase can be mistaken for β-glucosidase, since it hydrolyzes the chromogenic substrate p-nitrophenyl-β-D-glucoside (PNPG), although it does not hydrolyze other simple aryl and alkyl glucosides.