| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 90 === The purpose of this study is to purify and characterize chitosanase from crude enzyme preparation of papaya latex. Two chitosanase, named chitosanase I and II, were purified from commercial crude papain preparation by sequential steps of CM-Sepharose FF cation-exchange chromatography and Sephacryl S-100 HR gel filtration. By these steps, the purity of chitosanase I was increased 10.8-fold, with a yield of 4.0%, while the purity of chitosanase II was increased 13.2-fold, with a yield of 1.6%. Both chitosanases had a molecular weight of 27 kDa, as estimated by gel filtration. This value is close to the value that estimated by SDS-PAGE (28 kDa). Thus both chitosanases are monomeric enzymes. For chitosan (82% deacetylation) hydrolysis, chitosanase I had an optimal pH of 7 and an optimal temperature of 70°C, while chitosanase II had an optimal pH of 9 and an optimal temperature of 70°C. For hydrolysis of chitosans with varing N-acetyl content, both enzymes degraded 50 to 70% deacetylation chitosan most effectively. Both chitosanase had an isoelectric point of 10 to 11, as estimated by ion-exchange chromatography. Heavy metal ion of Hg2+ significantly inhibited while ions of Ni2+, Cu2+ and Zn2+ activated both enzyme activities.
|
|---|
