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EC Number

Catalytic Site Atlas

CSA LITERATURE entry for 1din

E.C. namecarboxymethylenebutenolidase
SpeciesPseudomonas knackmussii ()
E.C. Number (IntEnz)
CSA Homologues of 1din1zi6,1zi8,1zi9,1zic,1zix,3f67,
CSA Entries With UniProtID P0A115
CSA Entries With EC Number
PDBe Entry 1din
PDBSum Entry 1din
MACiE Entry 1din

Literature Report

IntroductionDienelactone hydrolase (DLHase) catalyses the hydrolysis of dienelactone to maleylacetate. This reaction is part of the beta-ketoadipate pathway used in bacteria and fungi to degrade aromatic compounds. Bacteria which utilise this pathway play an important role in the detoxification of many toxic halogenated aromatic compounds produced in industry. DLHase is a member of the alpha/beta hydrolase superfamily, although it does not possess a Ser-Hys-Asp catalytic triad and instead uses a triad of Cys-His-Asp.
MechansimDLHase uses a Cys-His-Asp catalytic triad. The acyl carbon of dienelactone is attacked by the nucleophilic Cys123 to form the first enzyme-substrate tetrahedral intermediate. This collapses, resulting in ring cleavage and expulsion of the heterocyclic oxygen to give an enolate intermediate. The enolate is protonated to give an acyl intermediate. The enzyme is deacylated by hydrolytic attack and general base catalysis, leading to release of the product.

Catalytic Sites for 1din

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
CysA123123macie:sideChainThe residue is stabilised in the thiolate form through the formation of a salt linkage with His202. The thiolate acts as a nucleophile towards the substrate lactone group, forming the first enzyme-substrate tetrahedral intermediate. The resulting substrate-enzyme acyl intermediate is then hydrolysed, giving maleylacetate and regenerating the active site.
AspA171171macie:sideChainThe negatively charged side chain is important in stabilising the positive charge of His202, facilitating the activation of the catalytic nucleophile Cys123.
HisA202202macie:sideChainThe imidazole group is implicated in activating Cus123 to form a thiolate, increasing its nucleophilic character. The residue's positive charge is stabilised through interactions with Asp171.
IleA3737macie:mainChainAmideThe residue's backbone forms an oxyanion hole which stabilises the negatively charged oxyanion intermediates and the transition states associated with them.
LeuA124124macie:mainChainAmideThe residue's backbone forms an oxyanion hole which stabilises the negatively charged oxyanion intermediates and the transition states associated with them.

Literature References

Pathak D
Thiol protease-like active site found in the enzyme dienelactone hydrolase: localization using biochemical, genetic, and structural tools.
Proteins 1991 9 267-279
PubMed: 1866431
Gupta HM
A novel computer modeling approach to the structures of small bioactive peptides: the structure of gonadotropin releasing hormone.
Proteins 1993 16 48-56
PubMed: 8497483