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

Non-enzymatic glycation is an irreversible posttranslational protein modification, which leads to a violation of physico-chemical properties and functions. Glycation most often affects lysine and arginine residues. Since hemoglobins contain many lysine residues (average 9%), they are often targets for 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 heart, 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 of sperm whale Mb and human Hb and 5 times higher than of horse Mb and bovine Hb. Lb glycation level depended on the presence of oxygen in the medium. Under microaerobic conditions, amount of AGEs formed was 3 times lower than in oxygen-containing environment, and the degradation of heme group was also slower. Glycation also affected the peroxidase activity of hemoproteins. Initial rate of Lb peroxidase reaction was 6 times higher than of myoglobins and 10–13 times higher than of hemoglobins. Glycation decreased the rate of Lb and hemoglobins peroxidase reaction, while for myoglobins it did not change or increased depending on incubation time with MG.