trpB

Gene Description

Tryptophan synthase beta chain (TrpB, EC 4.2.1.20), a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the final (beta) reaction of L-tryptophan biosynthesis, condensing indole with L-serine to yield L-tryptophan and water. PLP is bound as an internal aldimine to an active-site lysine (residue 95 in this protein). TrpB is a member of the fold-type II PLP enzyme family (TrpB family) and normally assembles with the alpha subunit (TrpA) into the alpha2-beta2 tryptophan synthase complex, in which the indole produced by TrpA from indole-3-glycerol phosphate is channeled directly to the TrpB active site through an intramolecular tunnel. TrpB carries out the terminal, fifth step of the conversion of chorismate to L-tryptophan and is a soluble cytoplasmic enzyme. In P. putida KT2440 the gene (PP_0083) is adjacent to and co-transcribed with trpA (PP_0082) as a trpBA operon, and its expression is strongly induced by indole.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0000162 L-tryptophan biosynthetic process	IEA GO_REF:0000120	ACCEPT	Summary: TrpB catalyzes the terminal step of L-tryptophan biosynthesis; this annotation correctly captures the core biological process. Reason: The protein is a UniProt-reviewed tryptophan synthase beta chain (EC 4.2.1.20) belonging to the TrpB family, with UniPathway UPA00035 (L-tryptophan biosynthesis, step 5/5). In P. putida KT2440 trpA disruption causes tryptophan auxotrophy, confirming the trpBA cluster is required for de novo tryptophan synthesis (PMID:21261884; see also file:PSEPK/trpB/trpB-deep-research-falcon.md). The IEA assignment is well-supported and represents a core function.
GO:0004834 tryptophan synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: Correct molecular function. TrpB is the tryptophan synthase beta subunit catalyzing the PLP-dependent beta-reaction (indole + L-serine -> L-tryptophan + H2O). Reason: Supported by EC 4.2.1.20, RHEA:10532, the conserved PLP-binding lysine (residue 95), HAMAP-Rule MF_00133, and TrpB-family InterPro/PANTHER signatures. This is the core enzymatic activity of the gene product.
GO:0005737 cytoplasm	IEA GO_REF:0000118	ACCEPT	Summary: Bacterial tryptophan synthase is a soluble cytoplasmic enzyme; cytoplasmic localization is correct. Reason: TrpB has no signal peptide or transmembrane region and functions in cytoplasmic amino-acid biosynthesis as part of the soluble alpha2-beta2 tryptophan synthase complex. The TreeGrafter IEA assignment is consistent with the well-established localization of this enzyme family. The term is somewhat generic but accurate for a bacterial cytosolic enzyme.

Core Functions

Catalyzes the PLP-dependent beta-replacement reaction forming L-tryptophan from indole (channeled from TrpA) and L-serine, completing the terminal step of L-tryptophan biosynthesis

Molecular Function:

tryptophan synthase activity

Directly Involved In:

L-tryptophan biosynthetic process

Cellular Locations:

cytoplasm

Supporting Evidence:

GO_REF:0000120
EC=4.2.1.20; tryptophan synthase activity inferred from InterPro, RHEA:10532, UniRule and PANTHER (TrpB family).
file:PSEPK/trpB/trpB-uniprot.txt
FUNCTION: The beta subunit is responsible for the synthesis of L-tryptophan from indole and L-serine. CATALYTIC ACTIVITY: indol-3-yl glycerol 3-phosphate + L-serine = D-glyceraldehyde 3-phosphate + L-tryptophan + H2O; PATHWAY: L-tryptophan from chorismate, step 5/5; COFACTOR: pyridoxal 5'-phosphate.

Gene Description

Existing Annotations Review

Core Functions

Catalyzes the PLP-dependent beta-replacement reaction forming L-tryptophan from indole (channeled from TrpA) and L-serine, completing the terminal step of L-tryptophan biosynthesis

References

Deep Research

Asta

Falcon

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