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. Author manuscript; available in PMC: 2019 Apr 17.
Published in final edited form as: Biotechnol J. 2010 Nov 4;6(3):300–305. doi: 10.1002/biot.201000282

Figure 2. 13C-Labeling experiment designed to elucidate central metabolic pathways in C. acetobutylicum.

Figure 2.

C. acetobutylicum is grown on [1,2-13C2]glucose as the sole carbon source (■=13C, □=12C). The expected labeling profiles and MIDs of intracellular metabolites at key points in metabolism are shown. Presence or absence of oxPPP is determined from the labeling of pyruvate. Condensation of M+2 labeled oxaloacetate and acetyl-CoA via CS will result in a characteristic pattern of M+2 and M+4 mass isotopomers of glutamate (m/z 432 fragment). To determine the stereochemistry of CS, MID of glutamate fragment m/z 330 is measured, which retains carbon atoms C2-C5. For Si-CS, MID of m/z 330 fragment of glutamate will be identical to that of m/z 432 fragment of glutamate; for Re-CS characteristic M+1 and M+3 isotopomers will be formed. To determine if the TCA cycle is complete, MID of fumarate is compared to that of glutamate fragment m/z 330 and aspartate.