Novel keto acid formate‐lyase and propionate kinase enzymes are components of an anaerobic pathway in <i>Escherichia coli</i> that degrades <scp>L</scp>‐threonine to propionate

Heßlinger, Christian; Fairhurst, Shirley A.; Sawers, R. Gary

doi:10.1046/j.1365-2958.1998.00696.x

Cited by 144 publications

(160 citation statements)

References 84 publications

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“…Whereas these organisms have a restricted metabolism, it is astonishing that E. coli is not able to grow on L-serine, although it has three L-SerDHs, encoded by sdaA (53), sdaB (50), and tdcG (15), which are subject to complex regulation by a number of different effectors (for a review, see reference 47). With the sdaA-overexpressing strain of C. glutamicum, we found growth on L-serine, albeit at a lower growth rate and final biomass yield than on pyruvate (data not shown).…”

Section: Discussionmentioning

confidence: 99%

Cometabolism of a Nongrowth Substrate:l-Serine Utilization byCorynebacterium glutamicum

Netzer

Peters‐Wendisch

Eggeling

et al. 2004

Appl Environ Microbiol

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C-labeled L-serine and analysis of cellularly derived metabolites by nuclear magnetic resonance spectroscopy revealed that the carbon skeleton of L-serine is mainly converted to pyruvate-derived metabolites such as L-alanine. The sdaA gene was identified in the genome of C. glutamicum, and overexpression of sdaA resulted in (i) functional L-serine dehydratase (L-SerDH) activity, and therefore conversion of L-serine to pyruvate, and (ii) growth of the recombinant strain on L-serine as the single substrate. In contrast, deletion of sdaA decreased the L-serine cometabolism rate with glucose by 47% but still resulted in degradation of L-serine to pyruvate. Cystathionine ␤-lyase was additionally found to convert L-serine to pyruvate, and the respective metC gene was induced 2.4-fold under high internal L-serine concentrations. Upon sdaA overexpression, the growth rate on glucose is reduced 36% from that of the wild type, illustrating that even with glucose as a single substrate, intracellular L-serine conversion to pyruvate might occur, although probably the weak affinity of L-SerDH (apparent K m , 11 mM) prevents substantial L-serine degradation.Cometabolism is often observed for xenobiotic compounds which do not enable growth as a single carbon-and energy source (21). This is due, for example, to long degradation pathways and unnatural structures. On the other hand, microorganisms with a restricted metabolism, such as Lactococcus lactis, are dependent on cometabolism of essential natural compounds, e.g., amino acids (35). The amino acid L-serine is characterized by the fact that several organisms have the ability to introduce it into the central metabolism via pyruvate (35,2,16). Another distinguishing feature is its high cellular demand, exceeding the simple provision of L-serine for protein synthesis, since L-serine is additionally required for glycine, cysteine, tryptophan, and phospholipid synthesis as well as for 1-carbonunit generation (52). Glycine, in turn, is a precursor for purines and heme. In Corynebacterium glutamicum about 7.5% of the total carbon flux toward L-serine is utilized for these purposes (28). Prior estimates for Escherichia coli determined that as much as 15% of the carbon assimilated from glucose involves L-serine (42). Due to the high demand and its key position in the precursor supply, L-serine has to be regarded as an intermediate of the central metabolism (52).In spite of the presence of L-serine dehydratase (L-SerDH) (47) and the key position of L-serine, growth of E. coli on L-serine as a carbon source is very poor, allowing doubling times of about 60 h only (63). When the organism is additionally exposed to low concentrations of glycine, isoleucine, and threonine, growth is enhanced (36). Interestingly, during growth on tryptone broth, where a number of amino acids are present, L-serine is utilized immediately and earlier than any other amino acid (43). Taken together, L-serine is clearly a poor growth substrate for E. coli and is preferably cometabolized. Klebsiella aerogenes and ...

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Section: Discussionmentioning

confidence: 99%

Cometabolism of a Nongrowth Substrate:l-Serine Utilization byCorynebacterium glutamicum

Netzer

Peters‐Wendisch

Eggeling

et al. 2004

Appl Environ Microbiol

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“…Since growth on low concentrations of acetate depends on AMP-ACS while growth on high concentrations requires the PTA-ACKA pathway, mutants that lack both cannot grow on acetate at any concentration (251). The inability to grow on acetate at any concentration argues against compensation by other acetate-activating enzymes, such as propionyl-CoA synthetase, encoded by prpE (201), or the propionate kinases, encoded by tdcD in E. coli or Salmonella enterica (186) or by pduW in S. enterica (52,331). PrpE can use acetate as an alternative substrate (201); thus, PrpE can restore growth on acetate to acs pta ackA mutants, but only when expressed from a high-copy-number plasmid and then only poorly (S. Kumari and A. J. Wolfe, unpublished data).…”

Section: Acetate Activation Pathwaysmentioning

confidence: 99%

The Acetate Switch

Wolfe

2005

Microbiol Mol Biol Rev

1,080

1,274

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To succeed, many cells must alternate between life-styles that permit rapid growth in the presence of abundant nutrients and ones that enhance survival in the absence of those nutrients. One such change in life-style, the “acetate switch,” occurs as cells deplete their environment of acetate-producing carbon sources and begin to rely on their ability to scavenge for acetate. This review explains why, when, and how cells excrete or dissimilate acetate. The central components of the “switch” (phosphotransacetylase [PTA], acetate kinase [ACK], and AMP-forming acetyl coenzyme A synthetase [AMP-ACS]) and the behavior of cells that lack these components are introduced. Acetyl phosphate (acetyl∼P), the high-energy intermediate of acetate dissimilation, is discussed, and conditions that influence its intracellular concentration are described. Evidence is provided that acetyl∼P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis. The merits of each mechanism proposed to explain the interaction of acetyl∼P with two-component signal transduction pathways are addressed. A short list of enzymes that generate acetyl∼P by PTA-ACKA-independent mechanisms is introduced and discussed briefly. Attention is then directed to the mechanisms used by cells to “flip the switch,” the induction and activation of the acetate-scavenging AMP-ACS. First, evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene. Next, the way in which cells regulate AMP-ACS activity through reversible acetylation is described. Finally, the “acetate switch” as it exists in selected eubacteria, archaea, and eukaryotes, including humans, is described

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“…The operon named tdcABC is a good example that highlights the power and the limitations of the method to predict transcription units. This operon has recently been shown to contain more members (16), changing the name of the operon to tdcABCDEFG. The genes tdcA and tdcB are kept together at high thresholds despite a distance of 98 bp between them (log-likelihood of 0.0493 to be in the same operon), because they belong to the same functional class (log-likelihood of 0.7192).…”

Section: Prediction Of Transcription Units In the E Coli Genomementioning

confidence: 99%

Operons in Escherichia coli : Genomic analyses and predictions

Salgado

Moreno–Hagelsieb

Smith

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

317

319

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The rich knowledge of operon organization in Escherichia coli, together with the completed chromosomal sequence of this bacterium, enabled us to perform an analysis of distances between genes and of functional relationships of adjacent genes in the same operon, as opposed to adjacent genes in different transcription units. We measured and demonstrated the expected tendencies of genes within operons to have much shorter intergenic distances than genes at the borders of transcription units. A clear peak at short distances between genes in the same operon contrasts with a flat frequency distribution of genes at the borders of transcription units. Also, genes in the same operon tend to have the same physiological functional class. The results of these analyses were used to implement a method to predict the genomic organization of genes into transcription units. The method has a maximum accuracy of 88% correct identification of pairs of adjacent genes to be in an operon, or at the borders of transcription units, and correctly identifies around 75% of the known transcription units when used to predict the transcription unit organization of the E. coli genome. Based on the frequency distance distributions, we estimated a total of 630 to 700 operons in E. coli. This step opens the possibility of predicting operon organization in other bacteria whose genome sequences have been finished.

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Novel keto acid formate‐lyase and propionate kinase enzymes are components of an anaerobic pathway in Escherichia coli that degrades L‐threonine to propionate

Cited by 144 publications

References 84 publications

Cometabolism of a Nongrowth Substrate:l-Serine Utilization byCorynebacterium glutamicum

Cometabolism of a Nongrowth Substrate:l-Serine Utilization byCorynebacterium glutamicum

The Acetate Switch

Operons in Escherichia coli : Genomic analyses and predictions

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