Biosynthesis of Menaquinone (Vitamin K2) and Ubiquinone (Coenzyme Q)

Meganathan, R.; Kwon, Ohsuk

doi:10.1128/ecosal.3.6.3.3

Cited by 38 publications

(71 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…To confirm this hypothesis, we used mutants lacking one or more quinone biosynthetic pathways (46). Specifically, as shown in Table 2, ubiCA mutants cannot make UQ (33,78,80), ubiE mutants cannot make UQ or MQ (36,77), and menA mutants cannot make MQ or DMQ (65,79).…”

Section: Resultsmentioning

confidence: 99%

Anaerobic Respiration of Escherichia coli in the Mouse Intestine

et al. 2011

View full text Add to dashboard Cite

The intestine is inhabited by a large microbial community consisting primarily of anaerobes and, to a lesser extent, facultative anaerobes, such as Escherichia coli, which we have shown requires aerobic respiration to compete successfully in the mouse intestine (S. A. Jones et al., Infect. Immun. 75:4891-4899, 2007). If facultative anaerobes efficiently lower oxygen availability in the intestine, then their sustained growth must also depend on anaerobic metabolism. In support of this idea, mutants lacking nitrate reductase or fumarate reductase have extreme colonization defects. Here, we further explore the role of anaerobic respiration in colonization using the streptomycin-treated mouse model. We found that respiratory electron flow is primarily via the naphthoquinones, which pass electrons to cytochrome bd oxidase and the anaerobic terminal reductases. We found that E. coli uses nitrate and fumarate in the intestine, but not nitrite, dimethyl sulfoxide, or trimethylamine N-oxide. Competitive colonizations revealed that cytochrome bd oxidase is more advantageous than nitrate reductase or fumarate reductase. Strains lacking nitrate reductase outcompeted fumarate reductase mutants once the nitrate concentration in cecal mucus reached submillimolar levels, indicating that fumarate is the more important anaerobic electron acceptor in the intestine because nitrate is limiting. Since nitrate is highest in the absence of E. coli, we conclude that E. coli is the only bacterium in the streptomycintreated mouse large intestine that respires nitrate. Lastly, we demonstrated that a mutant lacking the NarXL regulator (activator of the NarG system), but not a mutant lacking the NarP-NarQ regulator, has a colonization defect, consistent with the advantage provided by NarG. The emerging picture is one in which gene regulation is tuned to balance expression of the terminal reductases that E. coli uses to maximize its competitiveness and achieve the highest possible population in the intestine.The mouse colon is home to at least several hundred bacterial species and more than 100 billion bacteria per g of contents, a microbial community dominated by anaerobes with essentially no aerobes (2,38,57,68). It is becoming increasingly clear that facultative anaerobes consume oxygen and thereby modify their host environment. For example, kidney infection caused by uropathogenic Escherichia coli results in local ischemia (47). The facultatively anaerobic enteric pathogen Shigella flexneri responds to oxygen in the gut by modulating virulence gene expression (45). It has been postulated that the importance of Salmonella motility for chemotaxis through the mucus layer (61) may be due to aerotaxis (44). That E. coli requires cytochrome bd oxidase to gain a competitive advantage implies that the colon is not the anaerobic environment that many consider it to be (30). Here, we explore the possibility that efficient oxygen scavenging by E. coli in the intestine causes it to depend also on anaerobic respiration.To maximize their energy efficie...

show abstract

Section: Resultsmentioning

confidence: 99%

Anaerobic Respiration of Escherichia coli in the Mouse Intestine

et al. 2011

View full text Add to dashboard Cite

show abstract

“…E. coli predominantly uses ubiquinone-8 (UQ-8) in respiration under aerobic conditions (6,12) but produces menaquinone-8 (MK-8) and demethylmenaquinone-8 (DMK-8) as an obligatory electron carrier with fumarate, dimethylsufoxide, or trimethylamine N-oxide as the electron acceptor under anaerobic conditions (43,44). To examine the mutational effects on menaquinone biosynthesis, the mutants along with the parent strain were grown under anaerobic conditions in the presence of dimethyl sulfoxide for compositional analysis of the quinone pool.…”

Section: Resultsmentioning

confidence: 99%

“…The facultative anaerobe Escherichia coli has been used as a model bacterium for elucidation of the classical menaquinone biosynthetic pathway (12). Early studies of this pathway focused on the genetics of the biosynthesis, leading to identification of eight biosynthetic genes located at three loci, namely, menA, ubiE, and the menFDHBCE cluster.…”

mentioning

confidence: 99%

Identification of a Hotdog Fold Thioesterase Involved in the Biosynthesis of Menaquinone in Escherichia coli

Chen

et al. 2013

J Bacteriol

View full text Add to dashboard Cite

Escherichia coli is used as a model organism for elucidation of menaquinone biosynthesis, for which a hydrolytic step from 1,4-dihydroxy-2-naphthoyl-coenzyme A (DHNA-CoA) to 1,4-dihydroxy-2-naphthoate is still unaccounted for. Recently, a hotdog fold thioesterase has been shown to catalyze this conversion in phylloquinone biosynthesis, suggesting that its closest homolog, YbgC in Escherichia coli, may be the DHNA-CoA thioesterase in menaquinone biosynthesis. However, this possibility is excluded by the involvement of YbgC in the Tol-Pal system and its complete lack of hydrolytic activity toward DHNA-CoA. To identify the hydrolytic enzyme, we have performed an activity-based screen of all nine Escherichia coli hotdog fold thioesterases and found that YdiI possesses a high level of hydrolytic activity toward DHNA-CoA, with high substrate specificity, and that another thioesterase, EntH, from siderophore biosynthesis exhibits a moderate, much lower DHNA-CoA thioesterase activity. Deletion of the ydiI gene from the bacterial genome results in a significant decrease in menaquinone production, which is little affected in ⌬ybgC and ⌬entH mutants. These results support the notion that YdiI is the DHNA-CoA thioesterase involved in the biosynthesis of menaquinone in the model bacterium.

show abstract

“…The electron transfer chain of S. enterica, like that of the closely related bacterium Escherichia coli, possesses three different membrane quinones that mediate electron transfer between respiratory dehydrogenases and terminal reductases ( Fig. 1) (49,76). Ubiquinone (UQ) is the major quinone during aerobic growth, whereas the naphthoquinones menaquinone (MK) and demethylmenaquinone (DMK) are produced and used mainly during anaerobic respiration (for a review, see reference 75).…”

mentioning

confidence: 99%

Thiosulfate Reduction in Salmonella enterica Is Driven by the Proton Motive Force

et al. 2012

View full text Add to dashboard Cite

Thiosulfate respiration in Salmonella enterica serovar Typhimurium is catalyzed by the membrane-bound enzyme thiosulfate reductase. Experiments with quinone biosynthesis mutants show that menaquinol is the sole electron donor to thiosulfate reductase. However, the reduction of thiosulfate by menaquinol is highly endergonic under standard conditions (⌬E°= ‫؍‬ ؊328 mV). Thiosulfate reductase activity was found to depend on the proton motive force (PMF) across the cytoplasmic membrane. A structural model for thiosulfate reductase suggests that the PMF drives endergonic electron flow within the enzyme by a reverse loop mechanism. Thiosulfate reductase was able to catalyze the combined oxidation of sulfide and sulfite to thiosulfate in a reverse of the physiological reaction. In contrast to the forward reaction the exergonic thiosulfate-forming reaction was PMF independent. Electron transfer from formate to thiosulfate in whole cells occurs predominantly by intraspecies hydrogen transfer.

show abstract

Biosynthesis of Menaquinone (Vitamin K2) and Ubiquinone (Coenzyme Q)

Cited by 38 publications

References 37 publications

Anaerobic Respiration of Escherichia coli in the Mouse Intestine

Anaerobic Respiration of Escherichia coli in the Mouse Intestine

Identification of a Hotdog Fold Thioesterase Involved in the Biosynthesis of Menaquinone in Escherichia coli

Thiosulfate Reduction in Salmonella enterica Is Driven by the Proton Motive Force

Contact Info

Product

Resources

About