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Journal of Bacteriology, June 1999, p. 3562-3570, Vol. 181, No. 11
Laboratory of Structural Biology, National
Institute of Environmental Health Sciences, Research Triangle Park,
North Carolina 27709
Received 23 November 1998/Accepted 22 March 1999
We have evaluated the use of
[1,2-13C2]propionate for the analysis of
propionic acid metabolism, based on the ability to distinguish between
the methylcitrate and methylmalonate pathways. Studies using
propionate-adapted Escherichia coli MG1655 cells were
performed. Preservation of the
13C-13C-12C carbon skeleton in
labeled alanine and alanine-containing peptides involved in cell wall
recycling is indicative of the direct formation of pyruvate from
propionate via the methylcitrate cycle, the enzymes of which have
recently been demonstrated in E. coli. Additionally, formation of 13C-labeled formate from pyruvate by the
action of pyruvate-formate lyase is also consistent with the labeling
of pyruvate C-1. Carboxylation of the labeled pyruvate leads to
formation of [1,2-13C2]oxaloacetate and to
multiply labeled glutamate and succinate isotopomers, also consistent
with the flux through the methylcitrate pathway, followed by the
tricarboxylic acid (TCA) cycle. Additional labeling of TCA
intermediates arises due to the formation of
[1-13C]acetyl coenzyme A from the labeled pyruvate,
formed via pyruvate-formate lyase. Labeling patterns in trehalose and
glycine are also interpreted in terms of the above pathways. The
information derived from the [1,2-13C2]propionate label is contrasted with
information which can be derived from singly or triply labeled
propionate and shown to be more useful for distinguishing the different
propionate utilization pathways via nuclear magnetic resonance analysis.
0021-9193/99/$04.00+0
Carbon-13 Nuclear Magnetic Resonance Study of
Metabolism of Propionate by Escherichia coli
*
Corresponding author. Mailing address: MR-01,
Laboratory of Structural Biology, National Institute of Environmental
Health Sciences, Box 12233, Research Triangle Park, NC 27709. Phone: (919) 541-4879. Fax: (919) 541-5707. E-mail:
london{at}niehs.nih.gov.
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