Studies on relationships between the structure and the glycosidase-inhibiting activity of HPAAO and its analogs

p-Hydroxyphenylacetaldoxime (HPAAO) (anti and syn forms) obtained by fermentation and its analogs chemically synthesized were tested for their activities to inhibit various glycosidases. HPAAO inhibited bovine liver beta-galactosidase in a competitive manner at pH 7.0 with an apparent Ki value of 8 x 10(-8) M. HPAAO also inhibited various mammalian beta-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 beta-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.