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Title: Purification and characterization of corticosteroid side chain isomerase

Corticosteroid side chain isomerase of rat liver catalyzes the interconversion of the ketol (20-oxo-21-ol) and (20-hydroxy-21-al) forms of the corticosteroid side chain. The enzyme has now been purified to apparent homogeneity from rat liver cytosol by sequential chromatography on anionic, hydroxylapatite, and gel filtration columns. Ketol-aldol isomerization is followed by measuring the exchange of tritium from 21-tritiated steroids with water. The native enzyme is a dimer of MW 44,000. The isoelectric point is 4.8 {plus minus} 0.1 pH units. The purified enzyme is stimulated by Co{sup 3+} or Ni{sup 2+}. The enzyme utilizes 11-deoxycorticosterone, corticosterone, and 17-deoxycortisol as substrate but not cortisol, tetrahydrocortisol, and prednisolone. Tritium-water exchange of (21S)-(21-{sup 3}H)DOC is a pseudo-first-order reaction; 21-{sup 3}H exchange from the 21R isomer proceeds with first-order kinetics only after a lag associated with its epimerization to the 21S form.
Authors:
;  [1]
  1. (The Population Council, New York, NY (USA))
Publication Date:
OSTI Identifier:
6709441
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry; (USA); Journal Volume: 29:5
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; CORTICOSTEROIDS; CATALYSIS; ISOMERASES; MOLECULAR STRUCTURE; BIOCHEMICAL REACTION KINETICS; ELECTROPHORESIS; ENZYME ACTIVITY; LIVER; MICE; PURIFICATION; RATS; TRITIUM COMPOUNDS; ADRENAL HORMONES; ANIMALS; BODY; DIGESTIVE SYSTEM; ENZYMES; GLANDS; HYDROGEN COMPOUNDS; HYDROXY COMPOUNDS; KETONES; KINETICS; MAMMALS; ORGANIC COMPOUNDS; ORGANS; PREGNANES; REACTION KINETICS; RODENTS; STEROIDS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques