Sonawat H M
Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai.
Indian J Biochem Biophys. 1998 Oct;35(5):260-5.
Metabolism of 13C labeled substrates viz. glucose and pyruvate in S. cerevisiae has been studied by 13C Nuclear Magnetic Resonance Spectroscopy. C3-Pyruvate, alanine and lactate, and C2-acetate are produced from [1-13C]glucose. The pyruvate, entering TCA cycle, leads to preferential labeling of C2-glutamate. [2-13C]Glucose results in labeling of C2-pyruvate, alanine and lactate. Some C3-pyruvate is also produced, indicating the routing of the label from glucose through pentose phosphate pathway (PPP). In TCA cycle the C2-pyruvate preferentially labels the C3-glutamate. The NMR spectra, obtained with [2-13C]pyruvate as substrate, confirm the above observations. These results suggest that the intermediates of TCA cycle are transferred from one enzyme active site to another in a manner that allows only restricted rotation of the intermediates. That is, the intermediates are partially channeled.
利用¹³C核磁共振波谱法研究了酿酒酵母中¹³C标记底物（即葡萄糖和丙酮酸）的代谢情况。[1-¹³C]葡萄糖可生成C3-丙酮酸、丙氨酸和乳酸以及C2-乙酸盐。进入三羧酸循环的丙酮酸会导致C2-谷氨酸优先被标记。[2-¹³C]葡萄糖会使C2-丙酮酸、丙氨酸和乳酸被标记。还会产生一些C3-丙酮酸，这表明标记物从葡萄糖通过磷酸戊糖途径（PPP）进行了转运。在三羧酸循环中，C2-丙酮酸优先标记C3-谷氨酸。以[2-¹³C]丙酮酸作为底物获得的核磁共振谱证实了上述观察结果。这些结果表明，三羧酸循环的中间产物以一种仅允许中间产物有限旋转的方式从一个酶活性位点转移到另一个酶活性位点。也就是说，中间产物存在部分通道化现象。
