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 chitin synthase, an essential gene for hyphal growth, was obtained by RT-PCR and expressed in Saccharomyces cerevisiae by using the GAL1 promoter in a multicopy plasmid. The biochemical characteristics of chitin synthase B (ChsB) expressed in S. cerevisiae were examined. The chitin synthase B produced in galactose medium showed zymogenicity due to activation by trypsin treatment and required Mg2+ ion to exert maximal activity. It was competitively inhibited by polyoxin D. The Ki value of the inhibitor was 10 microM, 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 same as those of other chitin synthases.