An enzyme preparation from isolated beef liver mitochondria has the capacity to carry out all of the reactions of the tricarboxylic acid cycle when supplied with the essential precursors of acetylCoA, NAD+, FAD, GDP, and Pi2-.
Suppose that the acetyl-moiety of acetylCoA is labeled with the isotopes 13C in the methyl group and 14C in the carboxyl group. Thus,
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(carbon 13)H3- (carbon 14) - SCoA
Determine the radioactive labeling pattern in a-ketoglutarate after an infinite number of turns of the TCA cycle. Each turn of the cycle will bring a new labeled molecule of acetylCoA into the cycle. After an infinite number of turns of the cycle, a distinct pattern of label will be repeated in the molecule of a-ketoglutarate. What is the labeling pattern?