Abstract
We have studied the substrate specificities of a non-specific activator protein on the enzymatic hydrolyses of the following compounds: GM1 and GM2, as well as several of their derivatives including oligosaccharides, GgOse3Cer-II3-sulfate and LacCer-II3-sulfate, Gb-Ose3Cer and GbOse4Cer, three neolacto-series glycosphingolipids, and two non-ceramide glycolipids. Our results show that this activator protein has a broad spectrum of activity and exhibits the properties of a nonspecific natural detergent. The evidence of non-specificity was the ability of this activator protein to stimulate the hydrolyses of glycolipids, regardless of glycosphingolipids or non-ceramide glycolipids, carried out by glycosidases from animals, plants, and microorganisms. Its activity was, however, limited to substrates that had a lipid moiety. The oligosaccharide of GM1 and deacetyl-fatty acid free GM1 (II3-NeuGg-Ose4-sphingosine) were hydrolyzed by beta-galactosidase in the absence of this activator protein.
Highlights
GgOse’Cer-11’-sulfate and LacCer-11’-sulfate, GbOse’Cer and GbOse4Cer, three neolacto-series glycosphingolipids, and two non-ceramide glycolipids
In order to better understand the biologicalroles of the nonspecific activator protein which we called GM,activator previously [10, 11, 20], we have carried out systematic studies on the substrate specificities of this activator protein
Even the hydrolyses of dihexosylglycerolipids werereadily stimulated by this activatorprotein, despite their significant structural differences from gly
Summary
Ose4-sphingosine)were hydrolyzed by &galactosidase Our results show that minor alterations on the lipid moiety in the absence of this activator protein. The substrate and the enzyme deAcyl GM1 and the oligosaccharide derived from GM1) could for these reactions are glucosylceramide/@-glucosidase[4,5,6,7], be hydrolyzed by human hepatic @-galactosidasealone; the galactocerebroside sulfatide/arylsulfatase A [8, 9], GMl’/@- activator protein had no effect on these reactions. The abbreviations used are: GM1, I13NeuAc-GgOseaCerG: Ml(NeU), I13Neu-GgOserCedr;eAc-deAcyl-GMl, I13Neu-GgOse4-(longchain base); OligO-GMl, oligosaccharide derived from GMlG; M2, I13NeuAcon the assistance of an activator protein.
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