Channeling of TCA cycle intermediates in Saccharomyces cerevisiae.
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.
Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai.
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H M
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Sonawat
D002952:Citric Acid Cycle; D005947:Glucose / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D019289:Pyruvic Acid / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
D019289:Pyruvic Acid; D005947:Glucose