THE ENZYMATIC-HYDROLYSIS OF 6-ACYLAMINO-4-METHYLUMBELLIFERYL-BETA-D-GLUCOSIDES - IDENTIFICATION OF A NOVEL HUMAN ACID BETA-GLUCOSIDASE

Fluorogenic 6-acylamino-4-methylumbelliferyl-beta-D-glucosides were fo und to be poor substrates for the three known human beta-glucosidases, i.e., lysosomal and non-lysosomal glucocerebrosidases and cytosolic b road-specificity beta-glucosidase. However, homogenates of human tissu es and human cell types showed significant enzymatic hydrolysis of tha noylamino-4-methylumbelliferyl-beta-D-glucoside (EMGlc) due to the act ivity of a hitherto undescribed beta-glucosidase, called here EMGlc-as e. It was shown that the isozyme is hardly active towards 4-methylumbe lliferyl-beta-D-glucoside or glucosylceramide. EMGlc-ase exhibits maxi mal activity at pH 4.5 and 5.0 in the absence and presence of sodium t aurocholate respectively. It is a soluble lysosomal enzyme with a disc rete isoelectric point of about 5.0. EMGlc-ase is not inhibited by con duritol B-epoxide, is activated by sodium taurocholate and binds stron gly to Concanavalin A. This enzyme is not deficient in relation to Gau cher disease.