Inactivation of beta-fucosidase by iodine, N-acetylimidazole and tetranitromethane. Evidence for the existence of essential tyrosine residues.

beta-Fucosidase (beta-D-fucoside fucohydrolase, EC 3.2.1.38) isolated from the digestive juice of Achatina balteata is markedly inactivated when the enzyme is preincubated with three different probes, specific for tyrosine residues in the experimental conditions used. An effective protection against inactivation of the enzyme is obtained in the presence of a substrate analogue. These data strongly suggest that beta-fucosidase possesses essential tyrosine residues.