Darling T N, Blum J J
Dept. of Physiology, Duke University Medical Center, Durham, NC 27710.
Mol Biochem Parasitol. 1988 Mar;28(2):121-7. doi: 10.1016/0166-6851(88)90059-x.
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 dihydroxyacetone 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.
巴西利什曼原虫前鞭毛体在厌氧条件下培养时，可利用葡萄糖、核糖和甲基乙二醛产生D - 乳酸，但不能利用甘油、丙氨酸或丙酮酸，这表明存在乙二醛酶I和II，但不存在D - 乳酸脱氢酶。以下进一步证明了这一点：（1）在还原型谷胱甘肽存在的情况下，前鞭毛体超声裂解物可将甲基乙二醛转化为D - 乳酸；（2）前鞭毛体对苯乙二醛的利用速率与甲基乙二醛相当；（3）前鞭毛体在需氧条件下不利用外源提供的D - 乳酸。前鞭毛体超声裂解物可催化磷酸二羟丙酮转化为甲基乙二醛，这表明存在甲基乙二醛合酶。虽然在厌氧条件下从葡萄糖产生D - 乳酸的速率要高得多，但从甲基乙二醛产生D - 乳酸的速率与氧张力无关，这表明通过甲基乙二醛途径的通量控制发生在甲基乙二醛合酶处或之前。
