Expression of the β-1,3-Glucanase Gene in Yeast Hansenula Polymorpha.

The yeast cell wall is composed mainly of glucan, mannoprotein and chitin (1). In most yeasts, the polysaccharide glucan is predominantly β-1,3-linked with some branching via (3-1,6- linkages (2). The glucan network in the yeast cell wall, due to its rigidity, is an essential structure in preventing lysis of the protoplast in a hypotonic environment. Several microorganisms have been reported to produce extracellular enzymes capable of lysing yeast cells (3,4). Analysis of the constituents of these lytic enzyme preparations revealed the presence, among other activities, of β-1,3-glucanases (3,5). When combinedwith athiol reagent, β-1,3-glucanase alone was found to be able to lyse the yeast cell (6). Currently, the most common-used enzyme for digestion of yeast cell walls is an enzyme preparation called Zymolyase, produced from Oerskovia xanthineolytica (5). We have isolated the glucanase gene from this organism and completely determined its sequence (7). [ABSTRACT FROM AUTHOR]