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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1e3v

E.C. namesteroid Delta-isomerase
SpeciesPseudomonas putida (Bacteria)
E.C. Number (IntEnz) 5.3.3.1
CSA Homologues of 1e3vThere are 31 Homologs
CSA Entries With UniProtID P07445
CSA Entries With EC Number 5.3.3.1
PDBe Entry 1e3v
PDBSum Entry 1e3v
MACiE Entry M0349

Literature Report

IntroductionDelta-3-ketosteroid isomerase catalyses the cleavage of a steroid substrate C-4 H bond and the formation of a C-6 H bond via a dienolic intermediate. The mechanism proceeds at a diffusion controlled limit within an environment shielded from solvent.
MechansimThe residue Asp 40 acts as a base towards the steroid substrate, deprotonating the C3-OH group. The activation energy of proton transfer is reduced by the presence of Asp 102 and Tyr 16 which form strong low barrier hydrogen bonds to the dienolyic intermediate, interactions which are stronger than the hydrogen bonding between to the initial substrate. The proton is then relayed to C6, visa conjugate attack of the enolate at the catalytic residue.
Reaction

Catalytic Sites for 1e3v

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AspA4040macie:sideChainThe residue acts as a base towards the C3-OH group on the steroid substrate, and then a proton donor towards C6 in a conjugate attack from the dienolic substrate.
AspA100100macie:sideChainThe residue acts to stabilise the dienolic intermediate by forming low barrier hydrogen bonds. These interactions are also implicated in modifying the proton affinity of the substrate, allowing Asp 40 to act as a base at the alpha hydrogen to the carbonyl.
TyrA1616macie:sideChainThe residue acts to stabilise the dienolic intermediate by forming low barrier hydrogen bonds. These interactions are also implicated in modifying the proton affinity of the substrate, allowing Asp 40 to act as a base at the alpha hydrogen to the carbonyl.

Literature References

Notes:
Ha NC
Detection of large pKa perturbations of an inhibitor and a catalytic group at an enzyme active site, a mechanistic basis for catalytic power of many enzymes.
J Biol Chem 2000 275 41100-41106
PubMed: 11007792
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