The end of an old hypothesis: the pseudomonas signaling molecules 4-hydroxy-2-alkylquinolines derive from fatty acids, not 3-ketofatty acids.
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HAQ biosynthesis requires PqsABCD and proceeds in two steps; PqsBC carries out the second, condensing 2-ABA with an octanoate group carried on PqsC to form HHQ.
"HAQ biosynthesis, which requires the PqsABCD enzymes, proceeds by a two-step pathway: (1) PqsD mediates the synthesis of 2-aminobenzoylacetate (2-ABA) from anthraniloyl-coenzyme A (CoA) and malonyl-CoA, then (2) the decarboxylating coupling of 2-ABA to an octanoate group linked to PqsC produces HHQ, the direct precursor of PQS. PqsB is tightly associated with PqsC and required for the second step."
PqsBC, a Condensing Enzyme in the Biosynthesis of the Pseudomonas aeruginosa Quinolone Signal: CRYSTAL STRUCTURE, INHIBITION, AND REACTION MECHANISM.
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PqsBC is an obligate heterodimer; the catalytic active site (Cys-129, His-269) is contributed by PqsC.
"does not form a catalytic triad with His-269 and Cys-129, and in its place a valine (Val-299) is present"
Functions required for extracellular quinolone signaling by Pseudomonas aeruginosa.
pqsC review notes (BGC project) with predicted-complex evidence
Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping