Glycation of Leghemoglobin by Methylglyoxal in Comparison with Other Hemoglobins and the Influence on Peroxidase Activity

Nonenzymatic glycation is an irreversible posttranslational protein modification, which leads to a violation of physicochemical properties and functions. Glycation most often affects lysine and arginine residues. Since hemoglobins contain many lysine residues (average 9%), they are often targets for the glycating agents glyoxal and methylglyoxal (MG). A comparative study of the susceptibility for glycation of leghemoglobin (Lb) from bean nodules (Vicia faba L.), myoglobins (Mb) from sperm whale muscles and horse hearts, and hemoglobins (Hb) from bovine and human erythrocytes was carried out. The level of glycation was defined by the autofluorescence of protein-bound advanced glycation end products (AGEs). The glycation level of Lb was 2.5 times higher than that of sperm whale Mb and human Hb and five times higher than that of horse Mb and bovine Hb. The Lb glycation level depended on the presence of oxygen in the medium. Under microaerobic conditions, the amount of AGEs formed was three times lower than in an oxygen-containing environment, and the degradation of the heme group was also slower. Glycation also affected the peroxidase activity of hemoproteins. The initial rate of Lb peroxidase reaction was six times higher than that of myoglobins and 10–13 times higher than that of hemoglobins. Glycation decreased the rate of the Lb and hemoglobin peroxidase reaction, while for myoglobins it did not change or increased depending on thte incubation time with MG.