Howitz K T, McCarty R E
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
Plant Physiol. 1986 Feb;80(2):390-5. doi: 10.1104/pp.80.2.390.
The transport of glycolate and d-glycerate, the substrate and end product of the photorespiratory carbon pathway, respectively, by isolated intact pea (Pisum sativum) chloroplasts has been compared. d-Glycerate uptake was inhibited by the 2-hydroxymonocarboxylates, glycolate, glyoxylate, and d-lactate. Phosphate and phosphoglycerate and triose phosphates were without effect when the assays were carried out for two seconds. Glycolate was found to be a competitive inhibitor of d-glycerate uptake and the presence of glycolate in the chloroplast stroma strongly enhanced d-glycerate uptake from the medium. For optimal rates of d-glycerate-dependent O(2) evolution by pea chloroplasts, phosphate, ADP or ATP, and a mediator of cyclic electron flow had to be added. The inhibition of d-glycerate-dependent O(2) evolution by triose phosphates and 2-hydroxymonocarboxylates was tested. The inhibition of d-glycerate-dependent O(2) evolution by these metabolites did not correlate with their effects on glycerate transport. Thus, metabolism of d-glycerate, rather than its transport, limits the rate of glycerate-dependent oxygen evolution. The ramifications of d-glycerate metabolism on the interpretation of d-glycerate uptake data obtained with prolonged incubations are discussed. We conclude that d-glycerate and glycolate transport are mediated by the same transport system.
对完整分离的豌豆（Pisum sativum）叶绿体分别转运乙醇酸和甘油酸（光呼吸碳途径的底物和终产物）的情况进行了比较。甘油酸的摄取受到2-羟基单羧酸、乙醇酸、乙醛酸和d-乳酸的抑制。当测定时间为两秒时，磷酸盐、磷酸甘油酸和磷酸丙糖没有影响。发现乙醇酸是甘油酸摄取的竞争性抑制剂，叶绿体基质中乙醇酸的存在强烈增强了从培养基中摄取甘油酸的能力。为了使豌豆叶绿体以最佳速率依赖甘油酸进行氧气释放，必须添加磷酸盐、ADP或ATP以及循环电子流的介质。测试了磷酸丙糖和2-羟基单羧酸对依赖甘油酸的氧气释放的抑制作用。这些代谢物对依赖甘油酸的氧气释放的抑制作用与其对甘油酸转运的影响不相关。因此，甘油酸的代谢而非其转运限制了依赖甘油酸的氧气释放速率。讨论了甘油酸代谢对长时间孵育获得的甘油酸摄取数据解释的影响。我们得出结论，甘油酸和乙醇酸的转运由同一转运系统介导。
