Get   for     ? 
 Site search     ? 
Catalytic Site Atlas Version 2.2.12
Find Annotated Site: PDB code:
Swiss-Prot code:
EC number:
Help
CSA entry for 1qh5
Original Entry
Title:
Hydrolase
Compound:
Hydroxyacylglutathione hydrolase
Mutant:
No
UniProt/Swiss-Prot:
Q16775-GLO2_HUMAN
EC Class:
3.1.2.6
Other CSA Entries:
Overview of all sites for 1qh5
Homologues of 1qh5
Entries for UniProt/Swiss-Prot: Q16775
Entries for EC: 3.1.2.6
Other Databases:
PDB entry: 1qh5
PDBsum entry: 1qh5
UniProt/Swiss-Prot: Q16775
IntEnz entry: 3.1.2.6
Literature Report:
Introduction:
Glyoxalase II participates in the cellular detoxification of cytotoxic and mutagenic 2-oxoaldehydes. Glyoxalase I converts methylglyoxal (a cytotoxic byproduct of many cellular reactions) and glutathione into S-D-lactoylglutathione (SLG) which is also cytotoxic; the role of glyoxalase II is to hydrolyse SLG into D-lactic acid and glutathione.

Mechanism:
Glyoxalase II has a binuclear centre that has affinity for both Zn(II) and Fe(II) and is functional with either metal in either of its metal-binding sites.

1) Both metals coordinate a bridging hydroxide ion. This hydroxide nucleophile attacks the carbonyl carbon of the thioester group of SLG.

2) A tetrahedral transition state is formed. Metal 1 stabilises the negative charge forming on the thioester oxygen, and metal 2 stabilises the negative charge forming on the thioester sulphur (thus making the thiolate anion a better leaving group).

3) The tetrahedral intermediate collapses. Lactic acid and glutathione (still bound to metal 2 as a thiolate) are formed.

4) A terminal water molecule coordinated to metal 1 becomes coordinated to metal 2
as well. This a) releases the glutathione from metal 2 and b) acidifies the water enough to protonate the glutathione as it leaves. This leaves a new hydroxide ion in the active site.

Sites:

Click to Display Catalytic Site (Get help with this section)
Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ASPA 58 58Sidechain
ElectrostaticWater
Modifies the pKa of the hydroxide nucleophile which attacks the carbonyl carbon of the thioester group of SLG.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11085979 Related protein: O24496 Mutagenesis of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ZNA 261 0
ElectrostaticWater
ElectrostaticTransition state
Metal 1 acidifies the catalytic water molecule so that it exists as hydroxide in the active site. Metal 1 also stabilises the transition state by acting as an oxyanion hole for the thioester.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11085979 Related protein: O24496 Kinetic studies
PubMed ID 11085979 Related protein: O24496 Mutagenesis of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
ZNA 262 0
ElectrostaticTransition state
ElectrostaticWater
ElectrostaticSubstrate
Metal 2 acidifies the catalytic water molecule so that it exists as hydroxide in the active site. Metal 2 also stabilises the transition state by binding the sulphur atom of the thioester. This weakens the scissile S-C bond by making the glutathione moiety (as a thiolate) a good leaving group.
Evidence from paper Evidence concerns Evidence type
PubMed ID 11085979 Related protein: O24496 Mutagenesis of residue
PubMed ID 11085979 Related protein: O24496 Kinetic studies
Notes:
The conserved residue Asp 58 is proposed to have a role in positioning the nucleophilic hydroxide for attack, but whether it also modifies the pKa of this ion is less clear. There is evidence that it does not participate in a rate-limiting proton transfer.


References:
1
Crystal structure of human glyoxalase II and its complex with a glutathione thiolester substrate analogue.
A. D. Cameron and M. Ridderström and B. Olin and B. Mannervik
Structure Fold Des 7, (9) 1067-78, (1999).
10508780
2
Arabidopsis glyoxalase II contains a zinc/iron binuclear metal center that is essential for substrate binding and catalysis.
T. M. Zang and D. A. Hollman and P. A. Crawford and M. W. Crowder and C. A. Makaroff
J Biol Chem 276, (7) 4788-95, (2001).
11085979
3
Arabidopsis glyoxalase II contains a zinc/iron binuclear metal center that is essential for substrate binding and catalysis.
T. M. Zang and D. A. Hollman and P. A. Crawford and M. W. Crowder and C. A. Makaroff
J Biol Chem 276, (7) 4788-95, (2001).
11085979
Which EBI biological databases are available and how do I access them? EBI Site Map