Mechanism Of Mycoparasitism Of Monacrosporium Janus,a Nematode-trapping Fungus, In Respect Of Enzymology

The study revealed the mycoparasitisic mechanism of Monacrosporium janus, a parasitic fungus of both fungal sclerotium and nematodes, in respect of enzymology. Daily examination of activities of chitinases, proteinase, cellulase and glucanase showed that the glucanase were very strong and increased a lot when M. janus was inoculated in various liquid media, including the one using sclerotial powder as the sole carbon source. This indicated that glucanse played an important role in the process of the mycoparasitism.Studies on the optimum glucanase-producing conditions showed that initial pH 6, incubation for 4 days at 28 °C under 180rpm, and using bran powder as carbon source were appropriate for the production of the enzyme.The glucanase was purified via ammonium sulphate precipitation, sephadex G-25 gel filtration, and negative ion exchange, and confirmed by denatured gel electrophoresis. Its molecular mass is approximately 33 000 Dalton withN-terminal amino acid sequence NH₂ - N- P - C- Y- L- G-S-F-Q-T.The purified protein was characterized. Results showed that the optimum conditions for the glucanase activity were 70°C and pH5.0. The enzyme was stable when temperature was below 70°C and pH ranged 5-6. Ions Mn²⁺ and Co²⁺ were conducive to the enzyme activity, while ions Cu²⁺ and Fe³⁺ inhibitory to the enzyme activity significantly. When lamarian was used as substrate, the Km of the enzyme was 0.17mg/ml.Bioassay tests indicated that mycelium of Rhizoctonia solani AG1 became swellen, and finally broken down when treated with crude extract of glucanase, indicating that the glucanase might plays an important role in the process of mycoparasitism of M. janus. However, the isoenzyme purified in the study was not significantly inhibitory to the phytopathogens tested. The author discussed the possible reasons leading to the phenomenon.