The InterPro2GO mapping file assigns three GO terms to IPR009905 (2-vinyl bacteriochlorophyllide hydratase): GO:0016836 hydro-lyase activity, GO:0030494 bacteriochlorophyll biosynthetic process, and GO:0019685 photosynthesis, dark reaction. The first two fit the family; the third does not, because GO:0019685 is the carbon-fixation grouping term - its children are the Calvin cycle, C4 and CAM photosynthesis - and not the light-independent segment of the bacteriochlorophyll pathway. All four InterPro2GO rules that use GO:0019685 are light-independent (bacterio)chlorophyll-synthesis families, and QuickGO reports that all 3,731 GOA annotations to GO:0019685 cite GO_REF:0000002, so every use of the term in GOA descends from this one misreading (checked 2026-11-01).

UniProt maps the bchF entry to UniPathway UPA00671, porphyrin-containing compound metabolism / bacteriochlorophyll biosynthesis (light-independent), which yields GO:0036070. The pathway assignment agrees with the genetics: in R. capsulatus protochlorophyllide reduction is carried out in the dark by BchL/BchN/BchB.

A systematic directed mutational analysis of twelve open reading frames of the R. capsulatus 46 kb photosynthesis gene cluster. Mutations in seven of them abolished bacteriochlorophyll biosynthesis and caused accumulation of specific Mg-tetrapyrrole intermediates; four had no discernible pigment phenotype and one was partially disrupted. The cached record is abstract-only, and the abstract names no individual open reading frame.

That bchF is among the open reading frames mutated, and that its disruption causes accumulation of chlorophyllide a and 3-vinyl bacteriochlorophyllide a, is established indirectly: a 2023 study cites this paper (DOI 10.1006/jmbi.1994.1260, reference 3 of its Crossref reference list) as a source for the R. capsulatus bchF deletion phenotype.

This is the paper that defined the bchF locus. Pigments accumulated by strains carrying physically mapped transposon insertions were analysed spectroscopically and used to assign bchF, bchN, bchB and bchH, and bchF was identified as the bacteriochlorophyll a-specific enzyme that adds water across the vinyl group at the position now numbered C-3.

The pathway bchF serves runs in the dark in this organism: protochlorophyllide reduction is carried out by BchN, BchB and BchL rather than by a light-dependent reductase.

Places BchF in the bacteriochlorophyll a pathway as the 3-vinyl (bacterio)chlorophyllide a hydratase, acting either on 3-vinyl bacteriochlorophyllide a after chlorophyllide a reductase or on chlorophyllide a before it, with BchC oxidising the resulting 3-(1-hydroxyethyl) group to the 3-acetyl group of bacteriochlorophyllide a.

States the bchF deletion phenotype for both Rhodobacter species, citing (as its references 2-4) Bollivar et al. 1994 for the R. capsulatus result.

Direct enzymology on the BchF family: recombinant BchF (and its paralogue BchV) from Chlorobaculum tepidum, expressed in E. coli, catalyses hydration of the C3-vinyl group to a C3-1-hydroxyethyl group and runs the reaction in reverse, establishing the family as a stereoselective hydratase/dehydratase.

The assays were done on proteins from Chlorobaculum tepidum, not from Rhodobacter capsulatus, so this is orthologue-level rather than species-level evidence.

Paralogous 3-vinyl hydratases from Chlorobaculum tepidum, Chlorobaculum limnaeum, Chloroflexus aurantiacus and Chloracidobacterium thermophilum were all shown to be active hydratases in vitro, and the same 3-vinyl hydration step is identified as part of bacteriochlorophyll a biosynthesis.

The 3-vinyl hydration carried out by this enzyme family precedes the oxidation that installs the 3-acetyl group of bacteriochlorophyll a.

The entry assigns P26165 to the BchF family by three independent signatures (NCBIfam TIGR02020, Pfam PF07284, InterPro IPR009905) and places it in the light-independent bacteriochlorophyll biosynthesis pathway.

Protein existence is at the prediction level: no experiment on the P26165 protein itself is recorded, and the entry carries no CC FUNCTION, no catalytic activity, and no transmembrane features despite the sequence being strongly hydrophobic.