phthalein /3-D-glucuronide, p-nitrophenyl N-acetyl-/3-D-glucosaminide, p-nitrophenyl /3-D-fucoside, p- nitrophenyl /3-D-galactoside and 6-bromo-2-naphthyl /3-D-galactopyranoside from Sigma Chemical CO.(U.S.A..), phenyl /3-D-galactopyranoside from Nakarai

p-Hydroxyphenylacetaldoxime (HPAAO) (anti and syn forms) obtained by fermentation arid its analogs chemically synthesized were tested for their activities to inhibit various glycosidases. HPAAO inhibited bovine liver /3-galactosidase in a competitive manner at pH 17.0 with an apparent Ki value of 8 x 10-8 M. HPAAO also inhibited various mammalian /3.glycosidases which had pH optima between 6.0 and 8.0. The syn form of HPAAO was found to be more active than the anti form against bovine liver neutral /3-galactosidase. It was concluded that the oxime moiety of HPAAO and its analogs was essential for their enzyme-inhibiting activity and the activities of aromatic or aliphatic oxime derivatives were dependent on the number of carbon atoms in their alkyl-chains.