One of the major proteins of the Saccharomyces cerevisiae cell wall, a beta-glucanase (BGL2 gene product), has been isolated and purified to homogeneity under conditions for preserving enzyme activity. The study of enzyme properties of the protein revealed that it is an endo-beta-1,3-glucanase and not an exoglucanase as reported previously (F. Klebl and W. Tanner, J. Bacteriol. 171:6259-6264, 1989). The examination of the glucanase structure showed that the lower apparent molecular mass of the protein (29 kDa) compared with what was calculated from the amino acid sequence of the enzyme (33.5 kDa) is due to anomalous migration in sodium dodecyl sulfate gels and not to posttranslational processing of the polypeptide chain. Of two potential N glycosylation sites at Asn-202 and Asn-284, only the latter site is glycosylated. The overproduction of the beta-glucanase from the high-copy-number plasmid brought about a significant decrease in the growth rate of transformed yeast cells.