EC - Steroid Δ-isomerase

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IntEnz Enzyme Nomenclature


Accepted name:
steroid Δ-isomerase
Other names:
3-oxosteroid isomerase
Δ5(or Δ4)-3-keto steroid isomerase
Δ5-3-keto steroid isomerase
Δ5-3-oxosteroid isomerase
Δ5-ketosteroid isomerase
Δ5-steroid isomerase
hydroxysteroid isomerase
steroid isomerase
Δ5-3-ketosteroid isomerase
Systematic name:
3-oxosteroid Δ54-isomerase



May be at least three distinct enzymes.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004769
CAS Registry Number: 9031-36-1
UniProtKB/Swiss-Prot: (30) [show] [UniProt]


  1. Ewald, W., Werbein, H. and Chaikoff, I.L.
    Evidence for the presence of 17-hydroxypregnenedione isomerase in beef adrenal cortex.
    Biochim. Biophys. Acta 111: 306-312 (1965). [PMID: 5867327]
  2. Kawahara, F.S. and Talalay, P.
    Crystalline Δ5-3-ketosteroid isomerase.
    J. Biol. Chem. 235: PC1-PC2 (1960).
  3. Talalay, P. and Wang, V.S.
    Enzymic isomerization of Δ5-3-ketosteroids.
    Biochim. Biophys. Acta 18: 300-301 (1955).

[EC created 1961]