CHARACTERIZATION OF CHITINASE AND CHITOBIASE PRODUCED BY THE ENTOMOPATHOGENIC FUNGUS METARHIZIUM-ANISOPLIAE

Extracellular fluids from Metarhizium anisopliae grown on chitin as the sole carbon source contained distinct chitinase (pH optimum 5.3, MW 33 kDa) and chitobiase (pH optimum 5, MW 110 kDa, pI 6.4) activities. Chitinase activity was stabilized against extremes of pH and temperature by the presence of its chitin substrate. Chitinase fractions eluted from a sephadex column had activity against chitosan as well as locust cuticle chitin, crystalline chitin, and colloidal chitin. Products of enzymolysis were analyzed by descending paper chromatography. Chitinase had no activity against chitobiose, only trace activity against chitotriose, but preferentially cleaved chitotetraose in the middle bond releasing chitobiose. N-Acetyglucosamine was the major (vs colloidal chitin) or only (vs crystalline chitin) product detected following chitin hydrolysis. The chitobiase (also called β-N-acetylglucosaminidase) possessed simple glycosidase activity against p-nitrophenyl-acetylglucosaminide and hydrolyzed di-, tri-, and tetrasaccharides to N-acetylglucosamine. Chitobiase activity was significantly inhibited by its reaction product, N-acetylglucosamine. The mechanism of action of chitinolytic enzymes is discussed. © 1991.