Activation of Δ5-3-ketosteroid isomerase of bovine adrenal microsomes by serum albumins

Arthur Bertolino, Ann M. Benson, Paul Talalay

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The Δ5-3-ketosteroid isomerase (EC of bovine adrenal microsomes is activated as much as 10- to 20-fold by micromolar concentrations of bovine serum albumin. Comparable activations are observed with the serum albumins of 10 other mammalian species, but are not seen with ovalbumin or conalbumin. Evidence that the activation is attributable to the serum albumins, rather than to a small, firmly-bound ligand, is based on: (1) Failure to remove the stimulatory activity from the albumin by chloroform extraction, dialysis, or gel filtration; (2) Destruction of the activity by heating or by trypsin digestion; (3) Precipitation of the stimulatory activity of bovine serum albumin by specific antibody. Bovine serum albumin induces small decreases in the Michaelis constant for Δ5-androstene-3,17-dione, but most of the activational effect reflects an increase in the maximum velocity. Low concentrations of Triton X-100, which are without effect on the isomerase activity, prevent the activation by bovine serum albumin.

Original languageEnglish (US)
Pages (from-to)1158-1166
Number of pages9
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - Jun 13 1979

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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