Phosphorylation of human plasma alpha2-Heremans-Schmid glycoprotein (human fetuin) in vivo.

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Citation

Haglund AC, Ek B, Ek P

Phosphorylation of human plasma alpha2-Heremans-Schmid glycoprotein (human fetuin) in vivo.

Biochem J. 2001 Jul 15;357(Pt 2):437-45.

PubMed ID
11439093 [ View in PubMed
]
Abstract

A fraction of alpha2-Heremans-Schmid (alpha2-HS) glycoprotein (human fetuin) isolated from plasma was phosphorylated at serine-120 and serine-312 as shown by MS and peptide fragment sequencing after tryptic digestion. Serine-312-containing peptides were phosphorylated to 77% as determined from relative peak heights in the mass spectrum, which together with the phosphorylation of serine-120 implies a molar degree of phosphorylation of at least 1. Approximately 20% of the circulating fetuin plasma pool was phosphorylated to approx. 1 mol of phosphate/mol of protein. The remainder did not contain phosphate, resulting in an average phosphorylation degree for the protein in plasma of approx. 0.2 mol/mol. The isolated alpha2-HS glycoprotein was a heterodimer in which the entire C-terminal part of the connecting peptide including threonine-321 was present, but traces of C-terminally trimmed connecting peptide fragments were also found. The short B-chain was O-glycosylated to approx. 40%, whereas the N-glycosylation of asparagine-138 and asparagine-158 seemed to be 100%. This finding, for the first time, that circulating human plasma fetuin is partly phosphorylated, implies that the effects of phosphorylated alpha2-HS glycoprotein on insulin signal transduction seen in different cell systems could be relevant to its physiological function in vivo.

DrugBank Data that Cites this Article

Polypeptides
NameUniProt ID
Alpha-2-HS-glycoproteinP02765Details