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Corticosteroid side-chain isomerase in the circulatory system.
1Population Council, New York, NY 10021.
Steroids
|January 1, 1991
Summary
Corticosteroid side-chain (CSC) isomerase, an enzyme crucial for corticosteroid metabolism, is found across various species. Its presence in red blood cells suggests it’s both an intrinsic blood component and derived from tissues.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Corticosteroid side-chain (CSC) isomerase facilitates ketol-aldol interconversion in the corticosteroid side chain.
- Understanding the distribution and origin of CSC isomerase is important for corticosteroid metabolism research.
Purpose of the Study:
- To investigate the presence and species specificity of CSC isomerase in blood.
- To determine the cellular localization and potential origin of CSC isomerase in mouse blood.
Main Methods:
- Assessed CSC isomerase activity by measuring 3H-1H exchange of 21-tritiated corticosteroids (11-deoxycorticosterone, corticosterone, cortisol).
- Examined enzyme activity and performed immunostaining on mouse blood fractions (red blood cells, plasma, white blood cells).
- Investigated the adsorption of purified mouse liver CSC isomerase by red blood cells.
Main Results:
- CSC isomerase was detected in the blood of multiple species, including mouse, rat, guinea pig, chicken, pig, horse, sheep, cow, and human.
- Substrate specificity patterns for CSC isomerase varied significantly between species.
- In mouse blood, red blood cells exhibited the highest isomerase activity, followed by plasma, with white blood cells showing low and variable levels.
- Purified mouse liver CSC isomerase was found to bind to red blood cells.
Conclusions:
- Circulating corticosteroid side-chain isomerase appears to originate from both tissue sources and as an intrinsic component of blood.
- Red blood cells play a significant role in the presence and activity of CSC isomerase in circulation.