title: The principal site of nonenzymatic glycosylation of human serum albumin in vivo.
abstract: We have determined the major site of nonenzymatic glycosylation of human serum albumin in vivo. This was accomplished by reacting freshly purified human serum albumin with sodium [3H]borohydride followed by aminoethylation and tryptic digestion. The tryptic peptides were separated into a soluble fraction which contained 88% of the total 3H radioactivity and an insoluble fraction. In order to isolate the 3H-labeled glycosylated peptides, the soluble tryptic peptide fraction was first subjected to boronic acid affinity chromatography. Cation exchange chromatography then separated the soluble glycosylated peptides into a major peak which contained 48% of the total recovered 3H radioactivity and a number of minor peptide fractions. The amino acid composition of the major peptide was: Thr, Glu2, Ala, Val2, Leu2, Lys, lysino-1-deoxysorbitol. In accord with the primary structure of human serum albumin, this amino acid composition corresponds precisely to residues 525-534. Glucitol-lysine, the NH2-terminal residue of this peptide, is totally resistant to cleavage by trypsin. Thus, lysine-525 is the predominant site of nonenzymatic glycosylation of human serum albumin in vivo. Chromatography on GlycoGel B boronic acid affinity gel indicates that 10-12% of normal serum albumin is glycosylated. The rate of nonenzymatic glycosylation of this protein in vivo is approximately 9 times that of human hemoglobin.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001894:Borohydrides; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D005947:Glucose / Q000378:metabolism; D017127:Glycation End Products, Advanced; D006801:Humans; D010446:Peptide Fragments / Q000302:isolation & purification; D012709:Serum Albumin / Q000032:analysis / Q000378:metabolism*; D014357:Trypsin; D000093423:Glycated Serum Albumin
chemical_list: D000596:Amino Acids; D001894:Borohydrides; D017127:Glycation End Products, Advanced; D010446:Peptide Fragments; D012709:Serum Albumin; C025364:sodium borohydride; D014357:Trypsin; D005947:Glucose; D000093423:Glycated Serum Albumin