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ENZYME entry: EC

Accepted Name
(Phenol)carboxyphthiodiolenone synthase.
Reaction catalysed
  • 3 malonyl-CoA + 2 (S)-methylmalonyl-CoA + icosanoyl-[(phenol)carboxyphthiodiolenone synthase] + 5 NADPH <=> C(32)-carboxyphthiodiolenone-[(phenol)carboxyphthiodiolenone synthase] + 5 CoA + 5 NADP(+) + 5 CO(2) + 2 H(2)O
  • 3 malonyl-CoA + 2 (S)-methylmalonyl-CoA + docosanoyl-[(phenol)carboxyphthiodiolenone synthase] + 5 NADPH <=> C(34)-carboxyphthiodiolenone-[(phenol)carboxyphthiodiolenone synthase] + 5 CoA + 5 NADP(+) + 5 CO(2) + 2 H(2)O
  • 3 malonyl-CoA + 2 (S)-methylmalonyl-CoA + 19-(4-hydroxyphenyl)-nonadecanoyl-[(phenol)carboxyphthiodiolenone synthase] + 5 NADPH <=> C(37)-(phenol)carboxyphthiodiolenone-[(phenol)carboxyphthiodiolenone synthase] + 5 CoA + 5 NADP(+) + 5 CO(2) + 2 H(2)O
  • 3 malonyl-CoA + 2 (S)-methylmalonyl-CoA + 17-(4-hydroxyphenyl)heptadecanoyl-[(phenol)carboxyphthiodiolenone synthase] + 5 NADPH <=> C(35)-(phenol)carboxyphthiodiolenone-[(phenol)carboxyphthiodiolenone synthase] + 5 CoA + 5 NADP(+) + 5 CO(2) + 2 H(2)O
  • The enzyme, which is a complex of five polyketide synthase proteins, is involved in the synthesis of the lipid core common to phthiocerols and phenolphthiocerols.
  • The first protein, PpsA, can accept either a C(18) or C(20) long- chain fatty acyl, or a (4-hydroxyphenyl)-C(17) or C(19) fatty acyl.
  • The substrates must first be adenylated by EC, which also loads them onto PpsA.
  • PpsA then extends them using a malonyl-CoA extender unit.
  • The PpsB protein adds the next malonyl-CoA extender unit.
  • The absence of a dehydratase and an enoyl reductase domains in the PpsA and PpsB modules results in the formation of the diol portion of the phthiocerol moiety.
  • PpsC adds a third malonyl unit (releasing a water molecule due to its dehydratase domain), PpsD adds an (R)-methylmalonyl unit, releasing a water molecule, and PpsE adds a second (R)-methylmalonyl unit, without releasing a water molecule.
  • The incorporation of the methylmalonyl units results in formation of two branched methyl groups in the elongated product.
  • The enzyme does not contain a thioesterase domain, and release of the products requires the tesA-encoded type II thioesterase.
PRIAM enzyme-specific profiles2.3.1.292
KEGG Ligand Database for Enzyme Nomenclature2.3.1.292
IUBMB Enzyme Nomenclature2.3.1.292
MEDLINEFind literature relating to
Rhea expert-curated reactions2.3.1.292

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