Background: Non-enzymatic protein glycation is involved in structure and stability
changes that impair protein functionality, resulting in several human diseases, such as diabetes and
amyloidotic neuropathies (Alzheimer’s disease, Parkinson’s disease and Andrade’s syndrome).
Glyoxal, an endogenous reactive oxoaldehyde, increases in diabetes and reacts with several proteins
to form advanced glycation end products through Maillard-like reaction.
Objective: Human hemoglobin, the most abundant protein in blood cells is subjected to nonenzymatic
modification by reactive oxoaldehydes in diabetic condition. In the present study, the
effect of a low concentration of glyoxal (5 μM) on hemoglobin (10 μM) has been investigated
following a period of 30 days incubation in vitro.
Methods: Different techniques, mostly biophysical and spectroscopic (e.g. circular dichroism,
differential scanning calorimetric study, dynamic light scattering, mass spectrometry, etc.) were
used to study glyoxal-induced changes of hemoglobin.
Results: Glyoxal-treated hemoglobin exhibits decreased absorbance around 280 nm, decreased
fluorescence and reduced surface hydrophobicity compared to normal hemoglobin. Glyoxal
treatment enhances the stability of hemoglobin and lowers its susceptibility to thermal aggregation
compared to control hemoglobin as seen by different studies. Finally, peptide mass fingerprinting
study showed glyoxal to modify an arginine residue of α-chain of hemoglobin (Arg-31α) to
Conclusion: Increased level of glyoxal in diabetes mellitus as well as its high reactivity may cause
modifications of the heme protein. Thus, considering the significance of glyoxal-induced protein
modification under physiological conditions, the observation appears clinically relevant in terms of
understanding hydroimidazolone-mediated protein modification under in vivo conditions.