Purification and characterization of corticosteroid side chain isomerase

Journal Article · Tue Feb 06 00:00:00 EST 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00457a008· OSTI ID:6709441

Marandici, A; Monder, C ^[1]

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1. The Population Council, New York, NY (USA)

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.

• OSTI ID: 6709441
• Journal Information: Biochemistry; (USA), Vol. 29:5; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

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