Physiological and enzymological characterization of theβ-N-acetylhexosaminidase ofPenicillium chrysogenum

Abstract

Physiological and enzymological experiments indicated that the β‐N‐acetylhexosaminidase (HexN‐Ac'ase) of P. chrysogenum was most likely a vacuolar hydrolase, which was released into the culture medium during autolysis without modification. The formation of the enzyme was regulated solely by carbon source repression and ageing but was not induced by either chitin or N‐acetyl‐D‐glucosamine (GlcNAc). The selective inhibition of P. chrysogenum HexNAc'ase in vivo did not influence the growth, cell morphology and the HexNAc'ase production of the fungus. Substrate specificity investigations revealed that the purified P. chrysogenum HexNAc'ase hydrolysed N,N′‐diacetylchitobiose effectively but it was not active against N,N′,N″‐triacetylchitotriose and, surprisingly, did not liberate GlcNAc from β‐D‐galactosidase‐treated asialofetuin either. The HexNAc'ase of P. chrysogenum was subject to product inhibition by GlcNAc and possessed a homodimer quaternary structure with Mr, subunit = 66400.