MASS-SPECTROMETRIC ANALYSIS OF N-CARBOXYMETHYLAMINO ACIDS AS PERIODATE-OXIDATION DERIVATIVES OF AMADORI COMPOUNDS APPLICATION TO GLYCOSYLATED HEMOGLOBIN

Periodate oxidation of free and protein-bound Amadori compounds formed by the condensation of reducing sugars with primary amino groups generates, on acid hydrolysis, N-carboxymethyl derivatives of amino acids. The analysis of these modified amino acids may be used to estimate both the extent and the site of protein glycosylation. The present study describes the use of gas chromatography-mass spectrometry (GC/MS) and gas chromatography-tandem mass spectrometry (GC/MS/MS) for the identification of the various N-carboxymethylamino acids. Application of this approach to the quantitation of N-carboxymethylvaline and N(epsilon) carboxymethyllysine resulting from the oxidation of glycosylated haemoglobin is presented.