aroQ (PP_3003) encodes a type-II 3-dehydroquinate dehydratase (3-dehydroquinase, EC 4.2.1.10), a cytoplasmic enzyme of the shikimate pathway. It catalyzes the third step of chorismate biosynthesis, the dehydration of 3-dehydroquinate to 3-dehydroshikimate with release of water. Mechanistically, type-II dehydroquinases catalyze a trans (anti) dehydration through an enolate intermediate, in contrast to the Schiff-base mechanism of the unrelated type-I (aroD) enzymes. The protein adopts a flavodoxin-like fold and assembles as a homododecamer (four trimers). As a shikimate-pathway enzyme, it supplies chorismate, the common precursor of the aromatic amino acids (Phe, Tyr, Trp) and other aromatic metabolites such as folate precursors and ubiquinone.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003855 3-dehydroquinate dehydratase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Core molecular function. The protein belongs to the type-II 3-dehydroquinase family (HAMAP MF_00169, Pfam PF01220) and UniProt records the catalytic activity 3-dehydroquinate = 3-dehydroshikimate + H2O (RHEA:21096, EC 4.2.1.10), with conserved active-site residues (proton acceptor at position 24, proton donor at 102) consistent with the type-II dehydratase mechanism. Reason: Strongly supported by family/domain assignment, conserved catalytic residues, and the well-established function of bacterial type-II AroQ enzymes; this is the gene's core function. |
| GO:0009423 chorismate biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: 3-dehydroquinate dehydratase catalyzes step 3 of the 7-step chorismate biosynthesis (shikimate) pathway (UniPathway UPA00053, UER00086). This is the correct biological process context for the enzyme. Reason: Accurately captures the pathway role; consistent with UniProt PATHWAY annotation and the enzyme's molecular function. |
| GO:0019631 quinate catabolic process | IEA GO_REF:0000118 | MARK AS OVER ANNOTATED | Summary: This TreeGrafter (PANTHER PTHR21272) annotation propagates a quinate catabolism role. Type-II dehydroquinases occur in two physiological contexts the biosynthetic shikimate-pathway AroQ enzyme and a separate catabolic dehydroquinase (e.g., QuiC/QutE) of the quinate/shikimate utilization pathway. PP_3003 is the biosynthetic AroQ enzyme (HAMAP AroQ rule, aroQ TIGR01088, located within the shikimate-pathway context), not the dedicated quinate catabolic enzyme. While type-II DHQases share the same chemistry, assigning quinate catabolism to this specific protein over-extends the prediction. Reason: The catabolic process term is an over-propagation from a family-level phylogenetic grouping. The protein's verified role is biosynthetic (chorismate biosynthesis); there is no organism-specific evidence that PP_3003 functions in quinate catabolism, and that role is normally carried by a distinct enzyme. |
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