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 found to be poor substrates for the three known human beta-glucosidases, i.e., lysosomal and non-lysosomal glucocerebrosidases and cytosolic broad-specificity beta-glucosidase. However, homogenates of human tissues and human cell types showed significant enzymatic hydrolysis of 6-ethanoylamino-4-methylumbelliferyl-beta-D-glucoside (EMGlc) due to the activity of a hitherto undescribed beta-glucosidase, called here EMGlc-ase. It was shown that the isozyme is hardly active towards 4-methylumbelliferyl-beta-D-glucoside or glucosylceramide. EMGlc-ase exhibits maximal activity at pH 4.5 and 5.0 in the absence and presence of sodium taurocholate respectively. It is a soluble lysosomal enzyme with a discrete isoelectric point of about 5.0. EMGlc-ase is not inhibited by conduritol B-epoxide, is activated by sodium taurocholate and binds strongly to Concanavalin A. This enzyme is not deficient in relation to Gaucher disease.
Mikhaylova
M
M
Laboratory of Carbohydrate Chemistry, Institute of Biomedical Chemistry, Russian Academy of Medical Sciences, Moscow, Russia.
Wiederschain
G
G
Mikhaylov
V
V
Aerts
J M
JM
D000818:Animals; D002847:Chromatography, Agarose; D002850:Chromatography, Gel; D005347:Fibroblasts; D005453:Fluorescence; D005776:Gaucher Disease / Q000201:enzymology; D005960:Glucosides / Q000378:metabolism*; D005962:Glucosylceramidase / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007526:Isoelectric Point; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D051381:Rats; D013154:Spleen / Q000201:enzymology; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D001617:beta-Glucosidase / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*
D005960:Glucosides; C014110:4-methylumbelliferyl glucoside; D006923:Hymecromone; C101936:6-ethanoylamino-4-methylumbelliferyl-beta-glucosidase; D001617:beta-Glucosidase; D005962:Glucosylceramidase