Structure of the glycan portion of a pure sialoglyco-peptide fraction isolated from the skin of the fish labeo rohita

Abstract

The residue left after hot-water extraction of the defatted skin of the fish Labeo rohita has been found to contain sialoglycoprotein(s). On treatment with Pronase, this residue released all of the sialoglycopeptide (SGP) in 2 h. The resulting SGP was subjected to exhaustive, proteolytic treatment and several purification steps, where-upon it finally yielded a pure sialoglycopeptide (PSGP) fraction containing NeuAc, GlcNAc, Gal, Man, and Fuc in the molar ratios of 3.0:2.9:3.2:2.3:1.0, together with protein (10%). The major amino acid components of PSGP were aspartic acid, threonine, phenylalanine, and proline. From the results of base-borohydride treatment, methylation analysis, and enzymic reactions, a probable structure has been assigned to the glycan portion, which is linked through GlcNAc to Asn of the peptide core in PSGP.