Partial purification of a beef adrenal Δ5-3-ketosteroid isomerase and studies of its mechanism of action

S. Murota, C. C. Fenselau, Paul Talalay

Research output: Contribution to journalArticlepeer-review


The mechanism of isomerization of Δ5-androstene-3,17-dione to Δ4-androstene-3,17-dione has been examined with partially fractionated preparations of Δ5-3-ketosteroid isomerase (EC of beef adrenal microsomes. The enzyme is considerably more active at pH 9.0 than at pH 7.0. Studies on the mechanism of the enzymatic isomerization in D2O indicate that the reaction proceeds without significant isotope exchange between the medium and the steroid, and that it probably involves an intramolecular (or possibly an intermolecular) proton transfer from C-4 to C-6 in analogy with the Δ5-3-ketosteroid isomerase of Pseudomonas testosteroni. Possible reasons for the contrary results obtained by other investigators are discussed.

Original languageEnglish (US)
Pages (from-to)25-37
Number of pages13
Issue number1-5
StatePublished - 1971

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Endocrinology
  • Pharmacology
  • Clinical Biochemistry
  • Organic Chemistry

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