A bacterium producing chitinase was isolated from the dead body of Gymephorap ruoergensis. A chitinase was isolated from the culture of E. aerogenes and purified by means of ammonium sulfate precipitation, DEAE-cellulose column chromatography, and Sephadex G-100 column gel filtration. The purified chitinase showed homogeneity on the native polyacrylamide gel electrophoresis. Its molecular weight was estimated to be about 42.5 kD by SDS-PAGE. The optimum pH and temperature for hydrolysis of chitin were 6.0 and 55 degrees C respectively. Michaelis constant was 2.88 mg/mL. Different metal ions showed different effects on the chitinase activity, The chitinase activity was enhanced by Zn2+, Ba2+, Ca2+, Mn2+ and was strongly inhibited by Hg2+, Co2+, Mg2+.