[Substrate specificity of multiple forms of human alpha-D-galactosidase and alpha-D-fucosidase].

It was shown that human alpha-D-galactosidase is represented by multiple forms, only one of which can also split alpha-D-fucoside. Fabry's disease was found to be associated not only with the deficiency of the alpha-D-galactosidase total activity but also with the deficiency of the alpha-D-fucosidase activity. The decrease in the alpha-D-galactosidase activity is due to the lack of two enzyme forms, while the profile of alpha-D-fucosidase multiple forms during isoelectric focusing of human enzyme preparations is modified very little in comparison with the normal one. The deficiency of both enzymes was expressed in most degree in leukocytes as compared to other tissues. The residual activities of alpha-D-galactosidase and alpha-D-fucosidase in leukocytes were equal to 3.5 and 21%, respectively. Since the decrease in the alpha-D-fucosidase activity was not so noticeable as in the alpha-D-galactosidase activity, it may be expected that the determination of the alpha-D-fucosidase activity can no longer be regarded as a reliable test for the diagnosis of Fabry's disease. The data obtained suggest that alpha-D-galactoside and alpha-D-fucoside are split by the same enzyme, the multiple forms of which are characterized by selective specificity towards these substrates.