Methylglyoxal

Methylglyoxal, also called pyruvaldehyde or 2-oxopropanal (CH3-CO-CH=O or C3H4O2) is the aldehyde form of pyruvic acid. It has two carbonyl groups, so it is a dicarbonyl compound. Methylglyoxal is both an aldehyde and a ketone.

In organisms, methylglyoxal is formed as a side-product of several metabolic pathways. It may form from 3-aminoacetone, which is an intermediate of threonine catabolism, as well as through lipid peroxidation. However, the most important source is glycolysis. Here, methylglyoxal arises from nonenzymatic phosphate elimination from glyceraldehyde phosphate and dihydroxyacetone phosphate, two intermediates of glycolysis. Since methylglyoxal is highly cytotoxic, the body developed several detoxification mechanisms. One of these is the glyoxalase system. Methylglyoxal reacts with glutathione to form a hemithioacetal. This is converted into S- D -lactoyl-glutathione by glyoxalase I, and then further metabolized into D -lactate by glyoxalase II.

Why methylglyoxal is produced remains unknown, but research indicates it may be involved in the formation of advanced glycation endproducts (AGEs). In this process, methylglyoxal reacts with free amino groups of lysine and arginine and with thiol groups of cysteine, forming AGEs. Recent research has identified heat shock protein 27 (Hsp27) as a specific target of posttranslational modification by methylglyoxal in human metastatic melanoma cells.

Other glycation agents include the reducing sugars:
 * glucose, the sugar that stores energy
 * galactose, a part of milk sugar (lactose)
 * allose, an all-cis hexose carried into the cell by special proteins
 * ribose, a component of RNA.

Due to increased blood glucose levels, methylglyoxal has higher concentrations in diabetics, and has been linked to arterial atherogenesis. Damage by methylglyoxal to low-density lipoprotein through glycation causes a fourfold increase of atherogenesis in diabetics.

Methylglyoxal has been suggested to be a better marker than carboxymethyllysine (CML) for investigating the association between AGEs with adverse health outcomes.

Recently one mechanism of activity in humans of methylglyoxal has been identified. Methylglyoxal binds directly to the nerves responsible for pain registration and by that increases pain sensation.

Methylglyoxal is the main active component of manuka honey and accounts for the majority of this honey's antimicrobial activity.