Some Properties of Unpurified Chitinase from the Crayfish Plague Fungus, Aphanomyces astaci

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Abstract
The culture filtrate of the crayfish plague fungus, Aphanomyces astaci (Saprolegniaceae), incubated in a peptone glucose medium was tested for chitinase activity under different conditions. The activities were assayed turbidimetrically using low‐polymerized chitin as a substrate.Adsorption of chitinase was found to occur on chitin and probably on cellulose and sulphomethyl cellulose but not at all or only a little on some other cellulose derivatives.The pH optimum of the enzyme activity was found to lie at about pll 5.0–5.5. The stability was greatest near pH 6.5 and the highest degree of adsorption occurred at still higher pH values. Enzyme adsorption on the substrate seemed to protect the enzyme against inactivation by heating, shaking, and extreme pH‐conditions.The chitinase activity was positively affected by the rest of the culture filtrate.Mercury, cobalt, and copper chlorides, and to a lesser degree some other metal salts, lowered the enzyme activity when present in the test medium. Cellobiose, but neither glucose nor N‐acetyl glucosamine had a pronounced inhibiting effect on the activity. Neither cellobiose nor N‐acetyl glucosamine seemed to affect chitinase adsorption on chitin. Some chelating and reducing compounds inactivated the culture filtrate. This activity‐reducing effect of chelators was strongly prevented by EDTA in some cases.