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Abstract
A neutral serine protease (designated Aoz1) was purified to homogeneity from a strain of Arthrobotrys oligospora, obtained from soil in Yunnan Province. The purified protein showed a molecular mass of approximately 38 000 Dalton, pI 4.9 and displayed optimal activity at 45 C and pH 6–8. The protein could hydrolyze gelatin, casein and the chromogenic substrate azocoll, and it could immobilize nematodes in vitro (Panagrellus redivivus L. [Goodey]). The level of activity in culture medium was found to increase with increasing gelatin concentration. Scanning electron micrographs demonstrated dramatic structural changes in nematode cuticle treated with the purified protease. A partial peptide sequence obtained by N-terminal sequence analysis was used to design degenerate primers for the isolation of a cDNA gene encoding the mature protease. Analysis of the cDNA and corresponding genomic sequence revealed 97% identity with PII, a gene previously described from A. oligospora, and we conclude that this gene is likely a PII ortholog.
We would like to express special thanks to Dr. Wu Wenping, Ms. Tang Lan, Ms. Liu Ye, Ms. Duan Junxin and Ms. Geng Yang in the R & D center of Novozymes (China headquarters) for their kind help and valuable discussions, and especially for providing laboratory instruments to carry out part of this research work by Dr. Wu Wenping. The work was supported by the National Natural Science Foundation of China (approved number 30160004), Key Laboratory of Microbial Resources, Ministry of Education of China and by Yunnan Provincial Educational Fund (No. 2001–38). Associate Professor Zhou Wei and Ms. He Caiyun at Yunnan University are thanked for helping the research. We especially appreciate Ms. Mary Langlois of Mycologia for her good advice on our manuscript.