Structural study of the oligosaccharide moieties of sphingolipid activator proteins, saposins A, C and D obtained from the spleen of a Gaucher patient

Abstract

We have determined and compared the structures of the oligosaccharide moieties of saposin A, C and D purified from the spleen of a patient with Gaucher disease. These saposins, together with saposin B, are small glycoproteins, derived from separate domains of a single precursor, prosaposin, and are required for the lysosomal hydrolysis of various sphingolipids. The characteristic features of the oligosaccharide moieties of saposin A are (a) the predominance of a fucosylated trimannosyl core structure and (b) the occurrence of several different oligomannose‐type and N‐acetyllactosamine‐type oligosaccharides. Saposin C contains (a) a predominance of oligomannose‐type oligosaccharides and monoantennary oligosaccharides and (b) the presence of four different oligosaccharides having bisecting N‐acetylglucosamine residues (found only in this saposin). Saposin D is distinguished by the occurrence of oligomannose‐type oligosaccharides, which comprise nearly 90% of its total oligosaccharides. The possible reasons for the unique glycosylation of each saposin is discussed.

Expression of the Three Alternative Forms of the Sphingolipid Activator Protein Precursor in Baby Hamster Kidney Cells and Functional Assays in a Cell Culture System

“…3). All three SAP-precursors resulted in formation of mature SAP-A, SAP-B, SAP-C, and SAP-D, differing with respect to their carbohydrate types as analyzed previously (34,35). In our hands, mature SAP-A never yielded a clear band in its glycosylated form, but only a broad patch ranging from 14.5 to 29 kDa.…”

Solution Structure of Human Saposin C in a Detergent Environment

“…Saposins each contain a single N-glycosylation site, except for saposin A which has two. 5 However, extensively reported data suggest that the sugar moieties do not affect the function nor the membrane binding properties of the proteins. 6,7 Saposins each have six conserved cysteine residues forming three equivalent disulfide bridges that are essential for the function of the protein.…”

Isolation of proliferation factor of immature T‐cell clone in concanavalin A‐stimulated splenocyte culture supernatant

“…The apparent molecular weight of NPF, 16 000, was also comparable with that of saposin A (Figs 1 and 2). 13,14 Rat saposin A is composed of 84 amino acids highly glycosylated and identical to mouse saposin A except for two amino acids at the 23rd and 35th positions 15,16,22–24 . On the other hand, both rat and mouse TCGFs were active for the proliferation of N‐9F (unpublished data).…”