Characterization of a nonspecific activator protein for the enzyme hydrolysis of glycolipids

We have studied the substrate specificities of a non-specific activator protein on the enzymatic hydrolyses of the following compounds: G(M1) and G(M2), as well as several of their derivatives including oligosaccharides, GgOse₃Cer-II³-sulfate and LacCer-II³-sulfate, Gb-Ose₃Cer and GgOse₄Cer, 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 G(M1) and deacetyl-fatty acid free G(M1) (II³-NeuGg-Ose₄-sphingosine) were hydrolyzed by β-galactosidase in the absence of this activator protein.