Cell-free extracts and culture medium from Saccharomyces cerevisiae S288C contained the two glucan hydrolases that are known to be periplasmically located in vegetative cells of this yeast. These were an endo-1,3-β-glucanase and a much more abundant exo-1,3-β-glucanase. Cell-free extracts of strains carrying two different mutant alleles of the EXB1 gene were totally deficient in the latter enzyme, whereas the former appeared in multiple heterogeneous forms, probably due to incomplete glycosylation. In contrast, protoplast lysates of wild-type and exb1 mutant strains were identical in their complement of glucanases, which consisted of two enzymes clearly distinguishable from the periplasmic glucanases. One was an exo-1,3-β-glucanase, which was active on pustulan, p-nitrophenyl β-d-glucoside, salicin and cellobiose, and was of higher Mr than periplasmic exoglucanase. The other was a hydrolase acting on 1,3-β-glucan and 1,6-β-glucan but not the simple glucosides, which was not retained by DEAE-Biogel. Wild-type and exb1 mutant protoplasts secreted portions of the glucanases detected in protoplast lysates, when cultured in osmotically stabilized regeneration medium; the former also secreted the periplasmic exo-1,3-β-glucanase but the latter consistently failed to secrete it. It is concluded that the classically known glucanases of S. cerevisiae, located in the periplasmic space, must be formed as active enzymes, upon secretion, from inactive cytoplasmic precursors. On the other hand, the two new protoplast glucanases could be secreted by an alternative route that assures their incorporation into the wall structure, thus making their release into the culture medium more difficult.
HienM.H.,
FleetG.H.1983; Separation and characterization of six (1 →3)-β-glucanases from Saccharomyces cerevisiae. Journal of Bacteriology 156:1204–1213
LarribaG.,
VillaT.G.,
NebredaA.R.,
OliveroI.,
HernandezL.M.,
SanchezA.,
RamirezM.1984; Exo-glucanases in Saccharomyces cerevisiae: chemical nature, regulation, secretory pathway and cellular location. In Microbial Cell Wall Synthesis and Autolysis pp. 239–248NombelaC.
Edited by Amsterdam: Elsevier;
MolinaM.,
CenamorR.,
NombelaC.1987; Exo-l,3-β-glucanase activity in Candida albicans'. effect of the yeast-to-mycelium transition. Journal of General Microbiology 133:609–617
NebredaA.R.,
VillaT.G.,
VillanuevaJ.R.,
DelreyF.1986; Cloning of genes related to exo- β-glucanase production in Saccharomyces cerevisiae: characterization of an exo-β-glucanase structural gene. Gene 47:245–259
Del reyF.J.,
SantosT.,
Garcia-ACHAI.,
NombelaC.1979b; Synthesis of l,3-β-glucanases in Saccharomyces cerevisiae during the mitotic cycle, mating and sporulation. Journal of Bacteriology 139:924–931
DelreyF.J.,
SantosT.,
Garcia-AchaI.,
NombelaC.1980; Synthesis of jS-glucanases during sporulation in Saccharomyces cerevisiae: formation of a new, sporulation specific 1,3-β- glucanase. Journal of Bacteriology 143:621–627
SantosT.,
De lreyF.J.,
VillanuevaJ.R.,
NombelaC.1982; A mutation (exbl-1) that abolishes exo-l,3-β-glucanase production does not affect cell-wall dynamics in Saccharomyces cerevisiae. FEMS Microbiology Letters 13:259–263
SanzP.,
HerreroE.,
ValentinE.,
SentandreuR.1986; Una poblacion de proteinas de la pared de las levaduras es secretada independientemente de la ruta definida por los mutantes sec. Abstracts of III Reunion Conjunta de Micologla p. 94. Jarandilla de la Vera, Caceres, Spain: Sociedad Espaiiola de Microbiologia.
TomaszA.,
WbsterphalM.1971; Abnormal autolytic enzyme in a pneumococcus with altered teichoic acid composition. Proceedings of the National Academy of Sciences of the United States of America 68:2627–2630