PURIFICATION AND SOME PROPERTIES OF CHITINASE FROM ASPERGILLUS-CARNEUS

An extracellular chitinase from Aspergillus cerneus was purified by ammonium sulphate precipitation, gel filtration through Sephadex G-100, preparative HPLC chromatography and large slabs of polyacrylamide gel electrophoresis.The mol wt of the enzyme was estimated to be 25000 by SDS gel electrophoresis, and it contained 9.37% (w/w) carbohydrate residue, as glucose. The pattern of its amino acid composition showed high contents of asparagine, serine, and threonine. The enzyme was active at pH 5.2 and 50-degrees-C. The K(m) value of the enzyme was 4.37 mM (expressed as N-acetylglucosamine). The enzyme was stable at pH 3-9, whereas it was unstable at 70-degrees-C or more. Calcium and Mg ions slightly activated the enzyme, whereas Hg2+, I2, and p-chloromercuribenzoate inhibited the enzyme activity. The enzyme hydrolyzed chitin, colloidal chitin, glycol chitin, and chitooligsaccharides, but did not hydrolyze chitosan, starch, xylan, inulin, and cellulose. The lysis of A. niger and Micorcoccus lysodeikticus cell walls by the action of the enzyme was also investigated.