Methylglyoxal modification enhances the stability of hemoglobin and lowers its iron-mediated oxidation reactions: An...

Post-translational modification of proteins by Maillard reaction, known as glycation, is thought to be the root cause of different complications, particularly in diabetes mellitus and age-related disorders. Methylglyoxal (MG), a reactive α-oxoaldehyde, increases in diabetic condition and reacts with proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. In the present study, we have investigated the in vitro effect of methylglyoxal (200, 300μm) on the heme protein hemoglobin (HbA₀) (100μm) after incubation for one week at 25°C. Compared to HbA₀, MG-treated HbA₀ exhibited decreased absorbance around 280nm, reduced intrinsic fluorescence and lower surface hydrophobicity. MG treatment was not found to significantly affect the secondary structure of HbA₀. The stability of MG-treated HbA₀ was found to be higher compared to HbA₀. Moreover, H₂O₂-mediated iron release and subsequent iron-mediated oxidation (Fenton) reactions were found to be lower in presence of MG-treated HbA₀ compared to HbA₀. As shown by mass spectrometric studies, MG modified Arg-92α, Arg-104β, Arg-31α and Arg-40β of HbA₀ to hydroimidazolone adducts. The modifications thus appear to be associated with the observed structural alterations of the heme protein. Considering the increased level of MG in diabetes mellitus as well as its high reactivity, AGEs might be associated with structural and functional modifications of the protein including physiological significance.