GloB is a binuclear metal-dependent glyoxalase II that completes glutathione-dependent methylglyoxal detoxification. It hydrolyzes S-D-lactoylglutathione to D-lactate and regenerates glutathione after the GloA reaction. HAMAP predicts two zinc ions per subunit, but the physiological metal complement of Q88FF3 has not been determined directly.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004416 hydroxyacylglutathione hydrolase activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the defining glyoxalase II activity of GloB. Reason: Reviewed HAMAP, Rhea, catalytic-site, and exact family evidence support the assignment. Supporting Evidence: file:PSEPK/gloB/gloB-uniprot.txt Thiolesterase that catalyzes the hydrolysis of S-D-lactoyl- file:PSEPK/gloB/gloB-goa.tsv GO:0004416 hydroxyacylglutathione hydrolase activity |
| GO:0051596 methylglyoxal catabolic process | IEA GO_REF:0000120 | ACCEPT | Summary: GloB belongs to the specific glutathione-dependent route to D-lactate. Reason: This is the current valid process term; route specificity is retained in the core-function and reaction descriptions because the older GO:0019243 term is obsolete. Supporting Evidence: file:PSEPK/gloB/gloB-uniprot.txt (R)-lactate from methylglyoxal: step 2/2 |
| GO:0046872 metal ion binding | ISS file:PSEPK/gloB/gloB-uniprot.txt | NEW | Summary: GloB requires a binuclear metal center, but metal binding is ancillary to its substrate-specific hydrolase activity. Reason: The reviewed target record applies the GloB-specific HAMAP rule and projects two zinc ions plus eight zinc-ligand features. This establishes metal dependence, but it is not an experimental determination of the physiological metal complement of Q88FF3. The generic term is therefore proposed as non-core context rather than a metal-specific annotation. Supporting Evidence: file:PSEPK/gloB/gloB-uniprot.txt Binds 2 Zn(2+) ions per subunit. |
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Download this section (compressed HTML)Q: What is the physiological metal complement of native KT2440 GloB?
Q: Does the PTHR46233:SF3 metallo-beta-lactamase-superfamily protein PP_0772 hydrolyze S-lactoylglutathione in vivo or serve a different metallo-hydrolase role?
Experiment: Compare methylglyoxal turnover and S-lactoylglutathione accumulation in gloB, PP_0772, and double-deletion strains.
Type: targeted metabolomics and genetic epistasis
Q88FF3 is a reviewed KT2440 glyoxalase II with EC 3.1.2.6, Rhea 21864,
IPR017782, IPR035680, and PTHR43705:SF1
[file:PSEPK/gloB/gloB-uniprot.txt]. PP_0772/Q88PS6 instead belongs to
PTHR46233:SF3 and lacks the two GloB-specific InterPro signatures
[file:projects/P_PUTIDA/data/psepk_uniprot_metadata.tsv]. It is therefore an
untested metallo-beta-lactamase-superfamily candidate, not a second canonical
GloB-family protein.
The physiological importance of the second glyoxalase step may differ from its
clear catalytic role. In E. coli, a gloB deletion mutant was "as tolerant of
MG as the parent" despite impaired methylglyoxal turnover PMID:21143325. This result
does not challenge the Q88FF3 reaction assignment, but it motivates direct
testing of methylglyoxal tolerance and S-lactoylglutathione pools in KT2440.
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