REDUCTION OF METHEMOGLOBIN AND FERRICYTOCHROME-C BY GLYCOSYLATED AMINO-ACIDS AND ALBUMIN

The fraction of Amadori products gradually decreased during heavy glyc osylation of amino acids and human serum albumin while the amount of a colored product with the maximum fluorescence at 420 nm decreased. Th e addition of the produced ketoamines of amino acids to the solution o f native albumin quenched its own fluorescence due to generation of a Schiff base with amino groups of the protein. Carbonyl-containing Amad ori products obtained during the early steps of glycosylation were les s potent electron donors than amino acids more heavily modified by the carbohydrate. Under anaerobic conditions, glycosylated amino acids an d human serum albumin reduced metHb and ferricytochrome c to ferroform s. In the presence of oxygen, the electron was transferred from glycos ylated amino acids to ferriforms of the heme proteins and also to oxyg en molecules with the generation of superoxide anions and hydrogen per oxide. Free oxygen radicals and hydrogen peroxide induced damage to th e protein globule of Hb associated with the release of hemin, Fe(III) ions, and cleavage of the porphyrin ring.