Falcon (Edison Scientific) deep research report: hglS (PP_5260/ydcJ), Pseudomonas putida KT2440
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HglS catalyzes the Fe(II)-dependent conversion of 2-oxoadipate to D-2-hydroxyglutarate, a key step linking lysine catabolism to central metabolism.
"HglS is an **Fe(II)-dependent metalloenzyme** that converts **2-oxoadipate (2OA)** to **D-2-hydroxyglutarate (D-2HG)**"
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Mechanistic evidence (stoichiometric O2 consumption and double 18O incorporation) supports a coupled decarboxylation/oxygenation chemistry, consistent with the "2-oxoadipate dioxygenase/decarboxylase" naming.
"the transformation is described as an unusual decarboxylation/hydroxylation-like chemistry; associated mechanistic evidence indicates **O2 is consumed stoichiometrically with substrate** and isotopic labeling under **18O2** yields product containing **two 18O atoms**, consistent with incorporation from molecular oxygen."
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Genetic loss of hglS abolishes growth on lysine, establishing an essential in vivo role in lysine catabolism.
"A **ΔPP_5260 (ΔhglS)** deletion mutant **cannot grow on either lysine isomer**, establishing that HglS is necessary for lysine utilization in vivo and is not a minor side reaction."
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The product is the D-stereoisomer, assigned with a D-2HG-specific coupled assay.
"the stereochemistry was assigned using an **enzyme-coupled assay specific for D-2HG**, demonstrating formation of **D-2HG**."
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Iron(II) is the specific cofactor; activity is abolished by EDTA and reconstituted only by Fe(II).
"EDTA treatment abolished activity; after apo-enzyme preparation, **only Fe(II)** reconstituted catalysis."
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HglS is induced by lysine-pathway metabolites, consistent with a regulated catabolic role rather than housekeeping expression.
"PP_5260/YdcJ abundance is increased when *P. putida* is grown on **L-lysine, D-lysine, or 2-aminoadipate** relative to glucose, consistent with induction by lysine-pathway metabolites."
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The enzyme acts on soluble metabolites and is most defensibly assigned a cytosolic localization by inference (no direct localization experiment).
"the most defensible functional localization is **cytosolic** (inference, not direct experimental localization)."