lasI (PA1432, P33883) notes

No deep-research provider was available; this is a manual literature review
(PubMed MCP / E-utilities, cached abstracts). All cached papers below are
abstract-only.

Identity

UniProt P33883 (Swiss-Prot), LASI_PSEAE, 201 aa, acyl-homoserine-lactone
synthase, EC 2.3.1.184. Pfam PF00765 Autoind_synth; InterPro IPR001690;
PANTHER PTHR39322. Crystal structure 1RO5.
Reaction (UniProt CC CATALYTIC ACTIVITY, Rhea:10096): a fatty acyl-[ACP] +
S-adenosyl-L-methionine = an N-acyl-L-homoserine lactone +
S-methyl-5'-thioadenosine + holo-[ACP] + H+.

Literature

Passador et al. 1993 (PMID:8493556, PseudoCAP seed paper): lasI is needed for
high-level elastase (lasB) expression in gene-fusion experiments and is
"involved in the synthesis of a diffusible molecule termed Pseudomonas
autoinducer (PAI)" PMID:8493556.
The evidence the abstract describes is genetic (mutant/fusion phenotype);
the full text was not read, so whether it also has a direct assay is
unchecked. The abstract foregrounds production of a signal, not transduction
of one.
Pearson et al. 1994 (PMID:8278364): PAI purified from P. aeruginosa or from
E. coli carrying lasI is 3-oxo-C12-HSL PMID:8278364.
Hoang et al. 2002 (PMID:12480888): an in vitro fatty acid / 3-oxo-AHL
synthesis system with purified Fab proteins, ACP and LasI produced almost
exclusively 3-oxo-C12-HSL; "the LasI 3-oxo-AHL synthase is sufficient for
their synthesis" PMID:12480888. This is direct biochemical evidence for
GO:0061579 on the purified protein.
Gould et al. 2004 (PMID:15306017): crystal structure; LasI "produces
3-oxo-C12-AHL from the substrates 3-oxo-C12-acyl-carrier protein (acyl-ACP)
and S-adenosyl-L-methionine"; an acyl-chain tunnel and an acyl-ACP binding
surface (Arg154, Lys150) supported by in vivo reporter assays.

GO term reasoning

GO:0007165 signal transduction is defined to begin "with reception of a
signal" and, "For signaling between cells, signal transduction is restricted
to events at and within the receiving cell." LasI makes the ligand; LasR is
the receptor/transducer. LasI does no step of signal transduction, so the term
is wrong for LasI under CLAUDE.md's participation test (the entity that
performs the transduction steps is LasR, not LasI).
GO:0009372 quorum sensing: "The cell-cell signaling process in which
single-celled organisms ... [produce] small, diffusible, signal molecules,
detecting the concentration of these molecules, and triggering a signal
transduction pathway". Producing the signal is an explicit part of this
process, and LasI catalyses that step. Parents: cell-cell signaling
(GO:0007267, which covers "release of a ligand").
Comparator check (QuickGO, 2026-10-28): other autoinducer synthases do carry
quorum sensing with experimental evidence: the AinS-family AHL synthase G3FB25 (ainS, IDA,
PMID:10482519, CACAO) and LuxS (P45578 EcoCyc IMP; A1AEN2 CACAO IMP). RhlI
(P54291) and LuxI (P12747) carry only the IBA/TreeGrafter signal
transduction propagated from the same family, i.e. the same error, not an
independent convention. So quorum sensing is the term GO uses for signal
synthases.
No "N-acyl homoserine lactone biosynthetic process" term exists in GO (OAK
search of go.db). Not proposing a new term; the MF term GO:0061579 captures
the biosynthesis.
MF: GO:0061579 N-acyl homoserine lactone synthase activity is the right,
specific term. Currently only IEA (EC/Rhea); an IDA to
PMID:12480888 should be added upstream (recommended in the IEA row reason).

PseudoCAP IBA-seed assessment

PTN node	node term	n_seeds	leaf IBAs	seed annotation (term, evidence, PMID)	verdict	rationale
PTN002217335	GO:0007165 signal transduction	1 (sole seed)	5 (3 taxa; QuickGO lists lasI, rhlI, Yersinia yspI and ypeI, Bradyrhizobium bjaI)	GO:0007165 signal transduction, IDA, PMID:8493556 (PseudoCAP)	WRONG	LasI synthesises the diffusible autoinducer 3-oxo-C12-HSL; GO restricts signal transduction to events at and within the receiving cell, beginning with signal reception (LasR). The paper is a gene-fusion/mutant study (lasI needed for lasB expression and PAI synthesis), so IDA is also the wrong code. The correct process for a signal synthase is GO:0009372 quorum sensing (comparators AinS IDA, LuxS IMP). The IBD should be re-termed to quorum sensing; that term suits every LuxI-family AHL synthase leaf of the node. The node's MF, GO:0061579, is already on all leaves by EC/Rhea IEA.

Decisions summary

signal transduction IBA and IDA: MODIFY to GO:0009372 quorum sensing
(lateral correction; the gene makes the signal, it does not transduce it).
PSEUDOCAP WRONG_TERM (PROBABLE) on the IDA row and GO_CENTRAL WRONG_TERM
(PROBABLE) on the IBD at PTN002217335.
transferase activity IEA: MODIFY to GO:0061579.
N-acyl homoserine lactone synthase activity IEA: ACCEPT.
GO:0061579 has only IEA in GOA; an IDA to PMID:12480888 (purified LasI in a
reconstituted system) is recommended in the IEA row reason (a NEW row is not
allowed for a term already in GOA).