trpD

Gene Description

Anthranilate phosphoribosyltransferase (TrpD, EC 2.4.2.18), a cytosolic Mg2+-dependent enzyme that catalyzes the second committed step of L-tryptophan biosynthesis. It transfers the phosphoribosyl group of 5-phospho-alpha-D-ribose 1-diphosphate (PRPP) to anthranilate, producing N-(5-phospho-beta-D-ribosyl)-anthranilate (PRA) and diphosphate. In Pseudomonas putida KT2440 the enzyme is a monofunctional anthranilate phosphoribosyltransferase (the glutamine amidotransferase component of anthranilate synthase is encoded by a separate gene, trpG), belongs to the anthranilate phosphoribosyltransferase family (HAMAP MF_00211), and acts as a homodimer binding two magnesium ions per monomer. Loss of trpD function causes tryptophan auxotrophy that is rescued by L-tryptophan or indole, consistent with its position upstream of the indole/tryptophan branch in the chorismate-derived aromatic amino-acid biosynthetic route.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0000162 L-tryptophan biosynthetic process	IEA GO_REF:0000120	ACCEPT	Summary: TrpD catalyzes the second step of tryptophan biosynthesis (anthranilate to PRA). This is the core biological process for this gene, supported by the conserved pathway role and by experimental tryptophan auxotrophy of P. putida KT2440 trpD mutants. Reason: Correct core biological process. Consistent with the UniProt pathway annotation (L-tryptophan from chorismate, step 2/5) and with experimental auxotrophy/rescue evidence in KT2440.
GO:0000287 magnesium ion binding	IEA GO_REF:0000104	ACCEPT	Summary: The enzyme binds two Mg2+ ions per monomer, which assist PRPP binding. UniProt documents specific Mg2+ binding residues (positions 94, 227, 228). Reason: Magnesium is a required cofactor for this PRPP-dependent phosphoribosyltransferase; supported by HAMAP rule and modeled metal-binding sites.
GO:0004048 anthranilate phosphoribosyltransferase activity	IEA GO_REF:0000120	ACCEPT	Summary: This is the specific, defining molecular function of TrpD (EC 2.4.2.18), transferring the phosphoribosyl group of PRPP to anthranilate to form PRA. Reason: Core molecular function. Maps directly to EC 2.4.2.18 / RHEA:11768 and the anthranilate phosphoribosyltransferase family assignment (HAMAP MF_00211).
GO:0005829 cytosol	IEA GO_REF:0000118	ACCEPT	Summary: As a soluble biosynthetic enzyme in the tryptophan pathway, TrpD acts in the cytosol. No experimental localization in KT2440, but this is the parsimonious and family-consistent compartment. Reason: Appropriate cellular component for a cytoplasmic amino-acid biosynthetic enzyme; consistent with TreeGrafter inference across the family.
GO:0016757 glycosyltransferase activity	IEA GO_REF:0000002	MARK AS OVER ANNOTATED	Summary: This is a high-level grouping term derived from the InterPro "Glycosyl transferase family 3" domain. The actual activity is the more specific anthranilate phosphoribosyltransferase (a pentosyltransferase, GO:0016763 branch), already captured by GO:0004048. Reason: Uninformative parent term that does not accurately describe the enzyme's function; the specific activity (GO:0004048) and its proper parent pentosyltransferase (GO:0016763) are already annotated. Retaining glycosyltransferase activity is redundant and potentially misleading.
GO:0016763 pentosyltransferase activity	IEA GO_REF:0000117	KEEP AS NON CORE	Summary: Correct but general parent of the specific anthranilate phosphoribosyltransferase activity. EC 2.4.2.18 is a pentosyltransferase, so this term is accurate. Reason: True but uninformative relative to the specific GO:0004048 annotation; retain as a correct higher-level grouping rather than the core function.

Gene Description

Existing Annotations Review

Core Functions

Catalyzes the Mg2+-dependent transfer of the phosphoribosyl group of PRPP to anthranilate, producing N-(5-phospho-beta-D-ribosyl)-anthranilate (PRA), the second committed step of L-tryptophan biosynthesis.

References

Deep Research

Asta

Falcon

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