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Labeled pyruvate containing 14C ( 200 mCi/gm at ) C-3 ( the methyl carbon), 13 C

ID: 35146 • Letter: L

Question

Labeled pyruvate containing 14C ( 200 mCi/gm at ) C-3 ( the methyl carbon), 13 C( 90% enriched) at C-2 and 18 O ( 80%enriched) at C-2m was added to a pigeon breast muscle preparation, in order to investigate the citric acid cycle.

What will the labeling patern be ( both postion and extent of labeling ) in the isolated a- ketogluterate and in oxaloacetate ( Assume label enters onlin in the first turn ( ie pulse of labeled pyruvate is followed by a chase of unlabeled pyruvate.))

-- A ketoglutarate

18O

--- Oxaloacetate

18O

14 C

13 C

1st cycle 2nd cycle 3rd cycle

-- A ketoglutarate

18O

14 C 13 C

--- Oxaloacetate

18O

14 C

13 C

Explanation / Answer

1st

2nd

3rd

18 O

It will be incorporated at C1 position as

1st

2nd

3rd

  • Ketoglutarate

18 O

It will be incorporated at C1 position as