Enzyme - Hydroxyacylglutathione hydrolase

Alternative Name(s)
  • Glyoxalase II.

Catalytic Activity

S-(2-hydroxyacyl)glutathione + H2O = a 2-hydroxy carboxylate + glutathione + H(+)


There are no Cofactors for this Enzyme

Reaction Mechanism

    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.

    The substrate of this reaction is the product of Lactoylglutathione lyase, an enzyme which catalyses the initial steps in detoxifying methyl-glyoxyl. This enzyme regnerates the glutathione cofactor utilised by lactoylglutathione lyase.

    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. Both metals coordinate a bridging hydroxide ion. This hydroxide nucleophile attacks the carbonyl carbon of the thioester group of SLG. A tetrahedral intermediate 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). The tetrahedral intermediate collapses. Lactic acid and glutathione (still bound to metal 2 as a thiolate) are formed. Asp58 accepts a proton from the bridging oxygen to generate the lactate, this proton is then transferred to the thiolate to form glutathione. The products are released and new water bridges the zinc ions, the water is deprotonated by Asp58 regenerating the active site.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Asp Q16775 106 1qh5 58
    Asp Q16775 182 1qh5 134
    His Q16775 102 1qh5 54
    His Q16775 104 1qh5 56
    His Q16775 107 1qh5 59
    His Q16775 158 1qh5 110
    His Q16775 221 1qh5 173
    Step Components

    native state of cofactor regenerated, bimolecular nucleophilic addition, proton transfer, native state of enzyme regenerated, overall reactant used, unimolecular elimination by the conjugate base, overall product formed

    Step 1.

    Zinc activate water attacked the carbonyl carbon of the (R)-S-lactoylglutathione substrate in a nucleophilic addition, forming a tetrahedral intermediate.

    Step 2.

    The tetrahedral intermediate collapses releasing the (R)-lactate product and the thiolate form of glutathione. Asp58 accepts a proton from the bridging oxygen.

    Step 3.

    The thiolate of glutathione deprotonates Asp58, regenerating the glutathione cofactor used in the initial formation of hydroacetylglutathione.

    Step 4.

    Asp58 deprotonates a new bridging water molecule regenerating the active site. This proton can then be transferred from Asp58 to solution.


    The products of the reaction.

Reaction Parameters

  • Kinetic Parameters
    Organism KM Value [mM] Substrate Comment
    Salmonella enterica 1.8 S-D-lactoylglutathione at pH 7.5 and 30°C
    Plasmodium falciparum 11 S-D-lactoylglutathione mutant R257D, at 25°C, in 100 mM MOPS/NaOH, pH 6.8
    Leishmania infantum 180 S-D-lactoyltrypanothione wild type protein, pH not specified in the publication, temperature not specified in the publication
    Saccharomyces cerevisiae 710 S-D-mandeloylglutathione pH not specified in the publication, temperature not specified in the publication
    Oryza sativa 2000 S-Lactoylglutathione pH and temperature not specified in the publication
  • Temperature
    Organism Temperature Range Comment
    Cyberlindnera mrakii 25 - 55 25°C: about 60% of maximal activity, 55°C: about 70% of maximal activity
  • pH
    Organism pH Range Comment
    Oryza sativa 6 - 8
    Brassica juncea 6 - 8.5
    Nostoc sp. PCC 7120 = FACHB-418 6.5 - 8 enhanced enzyme activity in the pH range of 6.5-8.0
    Arabidopsis thaliana 7 - 9 saturation kinetic behavior for the thioester hydrolysis reaction. At pH 9.0 ligand exchange at the zinc center via deprotonation of the alpha-hydroxy group of the thioester to give an equilibrium amount of a zinc alkoxide species

Associated Proteins

Protein name Organism
Hydroxyacylglutathione hydrolase, cytoplasmic isozyme Baker's yeast
Hydroxyacylglutathione hydrolase 2, mitochondrial Mouse-ear cress
Probable hydroxyacylglutathione hydrolase C13B11.03c Fission yeast
Hydroxyacylglutathione hydrolase Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)
Hydroxyacylglutathione hydrolase GloC Escherichia coli (strain K12)