an extracellular chitinase (EC 3.2.1.14) was purified from the culture supernatant of Aspergillus sp. YJ-407 by precipitation with amonium sulfate followed by DEAE-cellulose (DE-52) chromato-graphy and preparative polyacrylamide gel electrophoresis.. Its molecular weight was estimated to be 41000 by SDS-PAGE, while its isoelectric point was pH 5.6. The enzyme was most active at pH 5 and 60 deg C , and it was strongly inhibited by Hg~+, Pb~(2+), Ag~+, F3~(2+), Mn~(2+). The enzyme was stable over a broad pH range 4-8 and below 45 deg C . Its Michaelis constant for colloidal chitin was 1. mg/ml.. The enzyme showed maximum activity towards ethylene glycol chitin and partially deacetyled chitosan as compared to collocidal chitin. With the analysis of the hydrolysis product, it was found the enzyme was an endochitinase. Chemical modification of the enzyme suggested that trptophyl and carboxyl groups were essential for the enzyme activity.
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