d-lactate production by Leishmania braziliensis through the glyoxalase pathway

Leishmania braziliensis promastigotes incubated anaerobically produce d-lactate from glucose, ribose, and methylglyoxal, but not from glycerol, alanine, or pyruvate, suggesting the presence of glyoxalases I and II but the absence of d-lactate dehydrogenase. Further support for this is shown by: (1) conversion of methylglyoxal to d-lactate in sonicates of promastigotes in the presence of reduced glutathione, (2) utilization of phenylglyoxal at rates comparable to methylglyoxal. (3) lack of utilization of exogenously supplied d-lactate by promastigotes under aerobic conditions. Sonicates of promastigotes catalyze the conversion of dihydroxy-acetone phosphate to methylglyoxal, suggesting the presence of methylglyoxal synthase. Whereas the rate of production of d-lactate from glucose is much greater under anaerobic conditions, the rate from methylglyoxal is independent of oxygen tension, indicating that control of flux through the methylglyoxal pathway occurs at, or before, methylglyoxal synthase.