Plasmalogen Biosynthesis by Anaerobic Bacteria: Identification of a Two-Gene Operon Responsible for Plasmalogen Production in Clostridium perfringens.
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The anaerobic plasmalogen pathway converts an ester to a vinyl ether reductively.
"anaerobic plasmalogen biosynthesis uses the reductive conversion of an ester to an aldehyde equivalent"
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E. faecalis EF1327 is a single-chain PlsA with all domains, and it alone confers plasmalogen synthesis on E. coli.
"The E. faecalis gene EF1327 encodes all activation and reduction/dehydration domains as a single polypeptide (PlsA)"
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Proposed mechanism, by analogy to BCR/HAD enzymes.
"The sequence would involve an initial reduction of the sn-1 linked ester to a ketyl radical anion, protonation, a second reduction-protonation sequence, and a final dehydration"
Characterization of plasmalogen production in facultative anaerobic bacteria and aerobic synthesis in recombinant Escherichia coli expressing anaerobic bacterium-derived plasmalogen synthase genes.
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Lactococcus cremoris strains produce plasmalogens. The cloned L. cremoris ATCC BAA-493 plsA (LACR_2543), 96.6% identical to Q9CDI2, confers plasmalogen synthesis on E. coli under both aerobic and anaerobic conditions.
"Both PlsLc and PlsBs produced plasmalogens, as evidenced by the detection of aldehydes in the lipid extracts after acid hydrolysis"
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The L. cremoris enzyme is unusually productive under aerobic conditions.
"the PlsLc strain produced more than three times the amount of plasmalogen as the other strains, even under aerobic conditions"
Characterization and heterologous expression of plasmalogen synthase MeHAD from Megasphaera elsdenii.
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The single-chain plasmalogen synthase MeHAD (M. elsdenii MELS_0169) is sufficient for plasmalogen synthesis in E. coli. A combined mutant of its four predicted [4Fe-4S] ligand cysteines is inactive. These cysteines align to Q9CDI2 C126, C165, C445 and C484.
"The four-cysteine (Cys125, Cys164, Cys445 and Cys484) site-mutant of MeHAD, which were predicted binding to the [4Fe-4S] cluster, was unable to synthesize plasmalogens"
Plasmalogen, a glycerophospholipid crucial for Streptococcus mutans acid tolerance and colonization.
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S. mutans SMU_438c, a single-chain PlsA, is required for plasmalogen production and is sufficient for it in a plasmalogen-negative streptococcus. (Its PANTHER subfamily, shared with Q9CDI2, comes from yxcA-bioinformatics, not from this paper.)
"The heterologous expression of SMU_438c in a plasmalogen-negative strain, Streptococcus sanguinis, resulted in the production of plasmalogen, indicating that this enzyme is sufficient for plasmalogen production"
Plasmalogens in bacteria, sixty years on.
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Review confirming that bacterial plasmalogens derive from diacyl lipids via the PlsA/PlsR reductases.
"The recent discovery of two genes encoding reductases that convert diacyl lipids to 1-alk-1′-enyl 2-acyl lipids"
yxcA (Q9CDI2) sequence comparison with characterized plasmalogen synthases
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Q9CDI2 is 96.6% identical to L. cremoris LACR_2543 and 67.3% identical to E. faecalis EF1327. Its residues 1011-1411 align to C. perfringens PlsR (Red2) at 41.3%, so the C-terminus is a fused Red2 domain that Pfam's HGD-D model misses.
"The local alignment of Q9CDI2 residues 1011-1411 to PlsR (41.3% identity over 402 columns) is the direct evidence that the C-terminal ~430 residues are the Red2 domain"
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The four MeHAD (G0VRE7) cysteines whose combined mutation abolishes plasmalogen synthesis (PMID:37348645) align to Q9CDI2 C126, C165, C445 and C484 in a global alignment (48.7% identity). All four are among the Act-region cysteines conserved in EF1327 and C. perfringens PlsA.
"All four Q9CDI2 positions are among the eight Act-region cysteines conserved in EF1327 and *C. perfringens* PlsA"