CHARACTERISTICS OF ASPARAGINE-LINKED SUGAR CHAINS OF SPHINGOLIPID ACTIVATOR PROTEIN-1 PURIFIED FROM NORMAL HUMAN LIVER AND GM1 GANGLIOSIDOSIS (TYPE-1) LIVER

Asparagine-linked sugar chains of sphingolipid activator protein 1 (SAP-1) purified from normal human liver and GM1 gangliosidosis (type 1) liver were comparatively investigated. Oligosaccharides released from the two SAP-1 samples by hydrazinolysis were fractionated by paper electrophoresis and by Aleuria aurantia lectin-Sepharose and Bio-Gel P-4 (under 400 mesh) column chromatography. Structures of oligosaccharides in each fraction were estimated from data on their effective molecular sizes, behavior on immobilized lectin columns with different carbohydrate-binding specificities, results of sequential digestion by exoglycosidases with different aglycon specificities, and methylation analysis. Sugar chains of SAP-1 purified from normal human liver and from GM1 gangliosidosis (type 1) liver were different from each other, although both of them were derived from complex-type sugar chains. The sugar chains of the former were the following eight degradation products from complex-type sugar chains by exoglycosidases in lysosomes: Manαl - 6(Manαl→3)Manβ1→4GlcNAc01→4GlcNAc0T, Manαl→6(Manαl→3)Manβ1→4GlcNAcβ1→4(Fucαl → 6)GlcNAc0T, Manαl→6Manβ1→4GlcNAcβ1→4GlcNAc0T, Manα1→6Manβ1→4GlcNAcβ1→4(Fucαl→6)GlcNAc0T, Manβ1 → 4GlcNAcβ?l→4GlcNAc0T, Manβ1→4GlcNAc/31→ 4(Fucαl→6)GlcNAc0T, GlcNAcβ1→ 4GlcNAc0T, and GlcNAc0T- In contrast to these, the sugar chains of the latter were sialylated and nonsialylated mono- to tetraantennary complex-type sugar chains that were not fully degraded due to a metabolic defect in acid/3-galactosidase activity. © 1990, American Chemical Society. All rights reserved.