Lactoylglutathione lyase

 

Lactoyl-glutathione lyase (or glyoxalase I) is part of the glyoxalase system which catalyses the conversion of acyclic alpha-oxoaldehydes into the corresponding alpha-hydroxyacids. Glyoxalase I catalyses the isomerization of the hemithioacetal (formed spontaneously from alpha-oxoaldehyde and GSH), to S-2-hydroxyacylglutathione (or R) derivatives, therefore decreasing the steady-state concentrations of physiological alpha-oxoaldehydes and associated glycation reactions. Physiological substrates of glyoxalase I are methylglyoxal, glyoxal and other acyclic alpha-oxoaldehydes.

This is the first of two steps in the conversion of 2-oxo-aldehydes to the corresponding 2-hydroxycarboxylic acids by way of the glyoxylase system. Methylglyoxal is produced as a by product of the triosephosphate isomerase reaction in glycolysis and, if not removed, is toxic as it reacts readily with with proteins and nucleic acids.

 

Reference Protein and Structure

Sequence
Q04760 UniProt (4.4.1.5) IPR004361 (Sequence Homologues) (PDB Homologues)
Biological species
Homo sapiens (Human) Uniprot
PDB
1qin - HUMAN GLYOXALASE I COMPLEXED WITH S-(N-HYDROXY-N-P-IODOPHENYLCARBAMOYL) GLUTATHIONE (2.0 Å) PDBe PDBsum 1qin
Catalytic CATH Domains
3.10.180.10 CATHdb (see all for 1qin)
Cofactors
Zinc(2+) (1) Metal MACiE
Click To Show Structure

Enzyme Reaction (EC:4.4.1.5)

methylglyoxal
CHEBI:17158ChEBI
+
glutathione
CHEBI:16856ChEBI
→
(R)-S-lactoylglutathione
CHEBI:15694ChEBI
Alternative enzyme names: Aldoketomutase, Glyoxylase I, Ketone-aldehyde mutase, Methylglyoxalase, Glyoxalase I, (R)-S-lactoylglutathione methylglyoxal-lyase (isomerizing),

Enzyme Mechanism

Introduction

This is the mechanism that occurs with the R enantiomer. The mechanism employed by the enzyme reflects the stereochemistry of the substrate. Both S and R forms of the hemithioacetal bind in the active site, coordinated to the Zn(II) metal in the place of previously coordinated water molecules.

The R enantiomer reaction mechanism differs in that it involves two bases (Glu99 and Glu172) as opposed to only one base in the S case (Glu172). The enzyme only works on the hemithioacetal intermediate which is formed by the spontaneous reaction between methylglyoxal and glutathione.

Both reaction mechanisms form a cis-ene-diol intermediate coordinated directly to the Zn centre. This intermediate then undergoes keto-enol tautomerisation, assisted by Glu172 in both mechanisms to form the R-2-hydroxyacylglutathione product.

Lactoylgutathione lyase I catalyses the first half of the mechanism to detoxify methyl-glyoxyl, where the product of this reaction is relayed to glyoxylase II (M0157) which catalyses the hydrolysis reaction to form D-lactate and glutathione.

Catalytic Residues Roles

UniProt PDB* (1qin)
Glu100 Glu99A The residue is correctly positioned to act as a general base towards the R substrate enantiomer. hydrogen bond acceptor, hydrogen bond donor, metal ligand, proton acceptor, proton donor
Glu173 Glu172B The residue is positioned correctly to act as a general base towards the S-substrate enantiomer. Glu172 then assists in the keto-enol tautomerisation of both enantiomers in the product forming stage of the reaction. hydrogen bond acceptor, metal ligand, proton acceptor, proton donor, proton relay
His127, Glu100, Glu173, Gln34 His126B, Glu99A, Glu172B, Gln33A Binds the Zn(II) ion. metal ligand
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

reaction occurs outside the enzyme, atom stereo change, cofactor used, assisted keto-enol tautomerisation, overall reactant used, intermediate formation, proton transfer, overall product formed, intermediate terminated, proton relay, native state of enzyme regenerated, native state of cofactor is not regenerated

References

  1. Cameron AD et al. (1999), Biochemistry, 38, 13480-13490. Reaction Mechanism of Glyoxalase I Explored by an X-ray Crystallographic Analysis of the Human Enzyme in Complex with a Transition State Analogue†. DOI:10.1021/bi990696c. PMID:10521255.
  2. Maroney MJ et al. (2014), Chem Rev, 114, 4206-4228. Nonredox Nickel Enzymes. DOI:10.1021/cr4004488. PMID:24369791.
  3. Suttisansanee U et al. (2011), Semin Cell Dev Biol, 22, 285-292. Bacterial glyoxalase enzymes. DOI:10.1016/j.semcdb.2011.02.004. PMID:21310258.
  4. Sukdeo N et al. (2007), Biochim Biophys Acta, 1774, 756-763. Pseudomonas aeruginosa contains multiple glyoxalase I-encoding genes from both metal activation classes. DOI:10.1016/j.bbapap.2007.04.005. PMID:17513180.
  5. Clugston SL et al. (2004), Biochem J, 377, 309-316. Investigation of metal binding and activation of Escherichia coli glyoxalase I: kinetic, thermodynamic and mutagenesis studies. DOI:10.1042/bj20030271. PMID:14556652.
  6. Thornalley PJ (2003), Biochem Soc Trans, 31, 1343-1348. Glyoxalase I--structure, function and a critical role in the enzymatic defence against glycation. PMID:14641060.
  7. Himo F et al. (2001), J Am Chem Soc, 123, 10280-10289. Catalytic Mechanism of Glyoxalase I:  A Theoretical Study. DOI:10.1021/ja010715h. PMID:11603978.
  8. Armstrong RN (2000), Biochemistry, 39, 13625-13632. Mechanistic Diversity in a Metalloenzyme Superfamily†. DOI:10.1021/bi001814v. PMID:11076500.
  9. Tamaki A et al. (2000), J Nat Prod, 63, 1417-1419. Phenolic Glycosides from the Leaves ofAlangiumplatanifoliumvar.platanifolium. DOI:10.1021/np000119l. PMID:11076566.
  10. Ridderström M et al. (1998), J Biol Chem, 273, 21623-21628. Involvement of an Active-site Zn2+ Ligand in the Catalytic Mechanism of Human Glyoxalase I. DOI:10.1074/jbc.273.34.21623. PMID:9705294.
  11. Sellin S et al. (1982), J Biol Chem, 257, 10023-10029. Nuclear relaxation studies of the role of the essential metal in glyoxalase I. PMID:7107595.

Step 1. Spontaneous formation of the lactoylglutathione.

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Catalytic Residues Roles

Residue Roles

Chemical Components

reaction occurs outside the enzyme, atom stereo change, cofactor used

Step 2. Glu99 deprotonates the C3 carbon adjacent to the sulfur atom, resulting in double bond rearrangement and formation of the enol-intermediate.

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Catalytic Residues Roles

Residue Roles
Glu99A hydrogen bond acceptor
Glu172B metal ligand, hydrogen bond acceptor
Glu99A metal ligand
Gln33A metal ligand
His126B metal ligand
Glu99A proton acceptor

Chemical Components

assisted keto-enol tautomerisation, atom stereo change, overall reactant used, intermediate formation, proton transfer

Step 3. The oxyanion deprotonates Glu99.

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Catalytic Residues Roles

Residue Roles
Glu99A hydrogen bond donor
Glu172B metal ligand, hydrogen bond acceptor
Glu99A metal ligand
Gln33A metal ligand
His126B metal ligand
Glu99A proton donor

Chemical Components

intermediate formation, proton transfer

Step 4. Glu172B deprotonates the C3 hydroxy group, causing double bond rearrangement and the protonation of C2 from Glu172B.

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Catalytic Residues Roles

Residue Roles
Glu99A hydrogen bond acceptor
Glu172B hydrogen bond acceptor, proton relay
Glu172B metal ligand
Glu99A metal ligand
Gln33A metal ligand
His126B metal ligand
Glu172B proton acceptor, proton donor

Chemical Components

assisted keto-enol tautomerisation, atom stereo change, overall product formed, intermediate terminated, proton relay, native state of enzyme regenerated, native state of cofactor is not regenerated, proton transfer
Download: Image, Marvin File

Step 1. Spontaneous formation of the lactoylglutathione.

Step 2. Glu99 deprotonates the C3 carbon adjacent to the sulfur atom, resulting in double bond rearrangement and formation of the enol-intermediate.

Step 3. The oxyanion deprotonates Glu99.

Step 4. Glu172B deprotonates the C3 hydroxy group, causing double bond rearrangement and the protonation of C2 from Glu172B.

Products.

Contributors

Gemma L. Holliday, Gail J. Bartlett, Daniel E. Almonacid, James W. Murray, Craig Porter, Katherine Ferris