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Investigation of the TCA cycle and the glyoxylate shunt in Escherichia coli BL21 and JM109 using 13 C‐NMR/MS
Author(s) -
Noronha S. B.,
Yeh H. J. C.,
Spande T. F.,
Shiloach J.
Publication year - 2000
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(20000505)68:3<316::aid-bit10>3.0.co;2-2
Subject(s) - glyoxylate cycle , citric acid cycle , citrate synthase , flux (metallurgy) , tricarboxylic acid , chemistry , isotopomers , biochemistry , metabolic flux analysis , escherichia coli , metabolism , organic chemistry , enzyme , molecule , gene
Acetate accumulation is a common problem observed in aerobic high cell density Escherichia coli cultures. A previous report has hypothesized that the glyoxylate shunt is active in a low acetate producer, E. coli BL21, and inactive in a high acetate producer, JM109. To further investigate this hypothesis, we now develop a model for the incorporation of 13 C from uniformly labeled glucose into key TCA cycle intermediates. The 13 C isotopomer distributions of oxaloacetate and acetyl‐CoA are first determined using NMR and MS techniques. These distributions are next validated by predicting the NMR spectrum of glutamate. Under steady state isotopic conditions, and with knowledge of the full isotopomer distributions of oxaloacetate and acetyl‐CoA, the flux ratios through the TCA cycle and the glycoxylate shunt are obtained with respect to the flux through the PPC anaplerotic shunt. We conclude that in BL21, the glyoxylate shunt is active at 22% of the flux through the TCA cycle, and is inactive in JM109. Further, in BL21, the flux through the TCA cycle equals the flux through the PPC shunt, while in JM109 the TCA cycle flux is only third of the flux through the PPC shunt. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 68: 316–327, 2000.