In vitro study on structural alteration of myoglobin by methylglyoxal.

Methylglyoxal (MG), a reactive α-oxoaldehyde, reacts with proteins to form irreversible advanced glycation end products (AGEs) following Maillard-like reaction. MG-induced AGE (MAGE) formation may be significant, particularly in diabetic condition with increased level of MG. Although myoglobin (Mb) is known to react with sugars to form AGEs, its interaction with MG is not known. Here we have studied interaction of Mb with MG. After in vitro reaction between Mb and MG at 25 °C for 7 days, the unchanged Mb and modified Mb (MG-Mb) were separated by ion exchange chromatography. Compared to Mb, MG-Mb exhibited higher electrophoretic mobility in native polyacrylamide gel electrophoresis, increased absorbance around 280 nm and more α-helical content, indicating structural changes of the modified protein. As shown by MALDI-mass spectrometry, MG converted Lys-16 and Lys-133 to carboxyethyllysine in MG-Mb. MAGE thus formed in MG-Mb may be associated with its enhanced mobility in native gel due to neutralization of positive charges and the observed structural changes in comparison with Mb.