The methylglyoxal pathway is activated by the increased intercellular uptake of carbon containing molecules such as glucose, glucose-6-phosphate, lactate, or glycerol.  Methylglyoxal is formed from dihydroxyacetone phosphate (DHAP) by the enzyme methylglyoxal synthase, giving off a phosphate group.
Methylglyoxal is then converted into two different products, either D-lactate, and L-lactate.  Methylglyoxal reductase and aldehyde dehydrogenase convert methylglyoxal into lactaldehyde and, eventually, L-lactate.  If methylglyoxal enters the glyoxylase pathway, it is converted into lactoylguatathione and eventually D-lactate.  Both D-lactate, and L-lactate are then converted into pyruvate.  The pyruvate that is created most often goes on to enter the Krebs cycle ([http://mic.sgmjournals.org/cgi/reprint/151/3/707 Weber] 711–13).