chsZ, a gene for a novel class of chitin synthase from Aspergillus oryzae

We cloned and characterized a novel Aspergillus oryzae chitin synthase gene, chsZ, encoding a polypeptide containing a new myosin motor-like domain in its N-terminal half. Alignment analysis revealed that ChsZ was less homologous to known class V enzymes, except for its probable chitin synthase conserved region in the C-terminal half. We also found a chsY gene and found that ChsY showed higher similarity to the class V enzymes than did ChsZ. Phylogenetic analysis clearly demonstrated that the A. oryzae ChsZ, together with Chs4 of Paracoccidioides brasiliensis and Chs6 of Ustilago maydis, formed a new subclass distinct from A. oryzae ChsY and known class V chitin synthases, including A. nidulans CsmA (ChsD) and A. fumigatus ChsE. In conclusion, we propose a new class, class VI chitin synthases, represented by A. oryzae ChsZ, P. brasiliensis Chs4 and U. maydis Chs6. Expression analysis suggested that the regulation of chsZ expression is distinct from that of chsY expression.