In organisms, methylglyoxal is formed as a side-product of several metabolic pathways. It may form from 3-amino acetone, which is an intermediate of threonine catabolism, as well as through lipid peroxidation. However, the most important source is glycolysis. Here, methylglyoxal arises from non enzymatic phosphate elimination from glyceraldehyde phosphate en 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 forming a hemithioacetal. This is converted into S-D-lactoyl-glutathione by glyoxalase I, and then further metabolised into D-lactate by glyoxalase II.
Why methylglyoxal is produced remains unknown, but several articles indicate that methylglyoxal is involved in the formation of advanced glycation endproducts (AGEs). In fact, methylglyoxal is proven to be the most important glycation agent (forming AGEs) . In this process, methylglyoxal reacts with free amino groups of lysine and arginine residues of proteins forming AGEs. Other glycation agents include reducing sugars like: