EC - (phenol)carboxyphthiodiolenone synthase

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IntEnz Enzyme Nomenclature


Accepted name:
(phenol)carboxyphthiodiolenone synthase
Systematic name:
(methyl)malonyl-CoA:long-chain acyl-[(phenol)carboxyphthiodiolenone synthase] (methyl)malonyltransferase {carboxyphthiodiolenone-[(phenol)carboxyphthiodiolenone synthase]-forming}



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 C18 or C20 long-chain fatty acyl, or a (4-hydroxyphenyl)-C17 or C19 fatty acyl. The substrates must first be adenylated by EC, long-chain fatty acid adenylase/transferase FadD26, 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 [2], and release of the products requires the tesA-encoded type II thioesterase [1].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
UniProtKB/Swiss-Prot: (14) [show] [UniProt]


  1. Rao, A., Ranganathan, A.
    Interaction studies on proteins encoded by the phthiocerol dimycocerosate locus of Mycobacterium tuberculosis.
    Mol. Genet. Genomics 272 : 571-579 (2004). [PMID: 15668773]
  2. Trivedi, O. A., Arora, P., Vats, A., Ansari, M. Z., Tickoo, R., Sridharan, V., Mohanty, D., Gokhale, R. S.
    Dissecting the mechanism and assembly of a complex virulence mycobacterial lipid.
    Mol. Cell 17 : 631-643 (2005). [PMID: 15749014]

[EC created 2019]