PROPERTIES OF YEAST EXPRESSED ASPERGILLUS-NIDULANS CHITIN SYNTHASE-B WHICH IS ESSENTIAL FOR HYPHAL GROWTH

A complementary DNA of the Aspergillus nidulans chsB gene encoding chi tin synthase, an essential gene for hyphal growth, was obtained by RT- PCR and expressed in Saccharomyces cerevisiae by using the GAL1 promot er in a multicopy plasmid. The biochemical characteristics of chitin s ynthase B (ChsB) expressed in S. cerevisiae were examined. The chitin synthase B produced in galactose medium showed zymogenicity due to act ivation by trypsin treatment and required Mg2+ ion to exert maximal ac tivity. It was competitively inhibited by polyoxin D. The K-i value of the inhibitor was 10 mu M, and the K-m for the substrate was 1.6 mM. The activity was enhanced by the addition of N-acetylglucosamine. The optimal pH is 7.5 when Mg2+ is used. These characteristics are the sam e as those of other chitin synthases.