Purification of an acid protease from Mucor rouxii that inactivates chitin synthetase.

An acid protease was purified from the mycelial form of Mucor rouxii by a method which involved salt and acid precipitation, gel filtration and anion-exchange chromatography. The enzyme had a molecular mass of 16,000 Da. Its optimum pH was 4.0, maximal activity was obtained at 50 degrees C, and it was inactivated at 70 degrees C. It was not affected by leupeptin or N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) but diazoacetyl-DL-norleucine methyl ester (DNME) in the presence of Cu2+ and more noticeably pepstatin A, strongly inhibited the activity. This acid protease did not activate "zymogenic" chitin synthetase from the fungus, but brought about its inactivation even at low concentrations and after short periods of incubation time.