A mass-spectrometric method for the estimation of the ratio of gamma-carboxyglutamic acid to glutamic acid at specific sites in proteins. Application to the N-terminal region of bovine prothrombin.
When a polypeptide containing gamma-carboxyglutamic acid is decarboxylated in 2H2O, residue of (gamma gamma-2H2)glutamic acid are formed. Subsequent proteolytic digestion produces peptides which contain at each site 2H2-substituted and unsubstituted glutamic acid in the same ratio as existed for gramma-carboxy-substitution. The peptides may be identified and this ratio determined by combined gas chromatography--mass spectrometry. We also discuss decarboxylation in 3H2O followed by amino-acid analysis and Edman degradation.
D015055:1-Carboxyglutamic Acid / Q000032:analysis*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D008401:Gas Chromatography-Mass Spectrometry; D005971:Glutamates / Q000032:analysis*; D008722:Methods; D010446:Peptide Fragments / Q000032:analysis; D011516:Prothrombin
D005971:Glutamates; D010446:Peptide Fragments; D015055:1-Carboxyglutamic Acid; D011516:Prothrombin