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A large form of renin from normal human kidney
The Journal of Clinical Endocrinology and Metabolism
|July 1, 1978
Summary
Human kidney renin exists in two forms: a larger precursor (58,000 daltons) and a smaller active form (43,000 daltons) found in plasma. These findings suggest the larger form may be a precursor to active renin.
Area of Science:
- Biochemistry
- Molecular Biology
- Renal Physiology
Background:
- Circulating human plasma renin has an apparent molecular size of 43,000 daltons.
- Understanding renin's molecular forms is crucial for studying the renin-angiotensin system.
- Previous research has established the size of plasma renin, but precursor forms remain less characterized.
Purpose of the Study:
- To characterize the molecular size of renin extracted from human kidney cortex.
- To investigate potential precursor forms of human renin.
- To compare the properties of different renin molecular species.
Main Methods:
- Renin extraction from human kidney cortex under varying conditions (protease inhibitors, freezing, pH).
- Determination of apparent molecular weight using Stokes' radius.
- Affinity chromatography using a substrate analog inhibitor.
- Enzyme activity assays and antibody inhibition studies.
Main Results:
- Renin extracted in low ionic strength buffer with protease inhibitors showed an apparent molecular weight of 58,000 +/- 3,000 daltons.
- Omitting protease inhibitors, multiple freeze-thaw cycles, or acidification to pH 2.8 revealed renin activity of 42,000 +/- 3,000 daltons.
- Both molecular forms bound to an affinity support with a specific substrate analog inhibitor.
- Antibody to the higher molecular weight form inhibited both forms equivalently.
Conclusions:
- The observations suggest that the larger form of renin (58,000 daltons) may represent a biosynthetic precursor.
- This precursor could exist as a zymogen or be part of an enzyme-binding protein complex.
- The findings provide insights into renin biosynthesis and potential regulation.