Lai J C, Sheu K F
Neurochem Res. 1987 Aug;12(8):715-22. doi: 10.1007/BF00970527.
The oxidation of pyruvate is mediated by the pyruvate dehydrogenase complex (PDHC; EC 1.2.4.1, EC 2.3.1.12 and EC 1.6.4.3) whose catalytic activity is influenced by phosphorylation and by product inhibition. 2-Oxoglutarate and 3-hydroxybutyrate are readily utilized by brain mitochondria and inhibit pyruvate oxidation. To further elucidate the regulatory behavior of brain PDHC, the effects of 2-oxoglutarate and 3-hydroxybutyrate on the flux of PDHC (as determined by [1-14C]pyruvate decarboxylation) and the activation (phosphorylation) state of PDHC were determined in isolated, non-synaptic cerebro-cortical mitochondria in the presence or absence of added adenine nucleotides (ADP or ATP). [1-14C]Pyruvate decarboxylation by these mitochondria is consistently depressed by either 3-hydroxybutyrate or 2-oxoglutarate in the presence of ADP when mitochondrial respiration is stimulated. In the presence of exogenous ADP, 3-hydroxybutyrate inhibits pyruvate oxidation mainly through the phosphorylation of PDHC, since the reduction of the PDHC flux parallels the depression of PDHC activation state under these conditions. On the other hand, in addition to the phosphorylation of PDHC, 2-oxoglutarate may also regulate pyruvate oxidation by product inhibition of PDHC in the presence of 0.5 mM pyruvate plus ADP or 5 mM pyruvate alone. This conclusion is based upon the observation that 2-oxoglutarate inhibits [1-14C]pyruvate decarboxylation to a much greater extent than that predicted from the PDHC activation state (i.e. catalytic capacity) alone. In conjunction with the results from our previous study (Lai, J. C. K. and Sheu, K.-F. R. (1985) J. Neurochem. 45, 1861-1868), the data of the present study are consistent with the notion that the relative importance of the various mechanisms that regulate brain and peripheral tissue PDHCs shows interesting differences.
丙酮酸的氧化由丙酮酸脱氢酶复合体（PDHC；EC 1.2.4.1、EC 2.3.1.12和EC 1.6.4.3）介导，其催化活性受磷酸化作用和产物抑制的影响。脑线粒体可轻易利用2-氧代戊二酸和3-羟基丁酸，并抑制丙酮酸氧化。为了进一步阐明脑PDHC的调节行为，在添加或不添加腺嘌呤核苷酸（ADP或ATP）的情况下，测定了2-氧代戊二酸和3-羟基丁酸对分离的非突触性大脑皮质线粒体中PDHC通量（通过[1-14C]丙酮酸脱羧测定）和PDHC的活化（磷酸化）状态的影响。当线粒体呼吸受到刺激时，在ADP存在的情况下，这些线粒体的[1-14C]丙酮酸脱羧始终会被3-羟基丁酸或2-氧代戊二酸抑制。在存在外源性ADP的情况下，3-羟基丁酸主要通过PDHC的磷酸化来抑制丙酮酸氧化，因为在这些条件下，PDHC通量的降低与PDHC活化状态的降低平行。另一方面，除了PDHC的磷酸化外，在存在0.5 mM丙酮酸加ADP或仅5 mM丙酮酸的情况下，2-氧代戊二酸还可能通过对PDHC的产物抑制来调节丙酮酸氧化。这一结论基于以下观察结果：2-氧代戊二酸对[1-14C]丙酮酸脱羧的抑制程度远大于仅根据PDHC活化状态（即催化能力）所预测的程度。结合我们之前研究（Lai, J. C. K.和Sheu, K.-F. R.（1985）J. Neurochem. 45, 1861-1868）的结果，本研究的数据与以下观点一致，即调节脑和外周组织PDHC的各种机制的相对重要性存在有趣的差异。
