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Only sphingolipid activator protein B (SAP‐B or saposin B) stimulates the degradation of globotriaosylceramide by recombinant human lysosomal α‐galactosidase in a detergent‐free liposomal system
Author(s) -
Kase Ryoichi,
Bierfreund Uwe,
Klein Andreas,
Kolter Thomas,
Itoh Kohji,
Suzuki Minoru,
Hashimoto Yasuhiro,
Sandhoff Konrad,
Sakuraba Hitoshi
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00863-0
Subject(s) - globotriaosylceramide , sphingolipid , activator (genetics) , recombinant dna , chemistry , biochemistry , liposome , enzyme , microbiology and biotechnology , biology , enzyme replacement therapy , receptor , medicine , disease , pathology , gene
The degradation of globotriaosylceramide (GbOse 3 Cer) by insect‐cell derived recombinant human α‐galactosidase (EC 3.2.1.22) was carried out in a detergent‐free liposomal system in order to mimic intralysosomal conditions. GbOse 3 Cer incorporated into unilamellar liposomes was used as the substrate, and naturally occurring sphingolipid activator proteins, rather than detergents, were used to stimulate the enzyme reaction. The degradation of GbOse 3 Cer was dependent on the presence of both α‐galactosidase and sphingolipid activator protein B (SAP‐B or saposin B). It proceeded optimally at pH 4.6, and was enhanced by increasing amounts of both α‐galactosidase (0.24–24 mU/50 μl assay) and SAP‐B (0–5 μg/50 μl assay). The enzyme reaction was not affected by SAP‐A, SAP‐C, or SAP‐D. Therefore, our results indicate that only SAP‐B is essential for the degradation of GbOse 3 Cer by α‐galactosidase.