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Angiotensin I-converting enzyme in human urine.
Clinica Chimica Acta; International Journal of Clinical Chemistry
|November 1, 1978
Summary
Human urine contains angiotensin I-converting enzyme (ACE), with activity linked to sodium excretion. This urinary ACE shares properties with lung ACE, suggesting potential diagnostic applications.
Area of Science:
- Biochemistry
- Urology
- Enzymology
Background:
- Angiotensin I-converting enzyme (ACE) plays a crucial role in the renin-angiotensin system.
- ACE activity is primarily associated with the lungs and vascular endothelium.
- The presence and significance of ACE in human urine were not well-established.
Purpose of the Study:
- To determine if angiotensin I-converting enzyme (ACE) is excreted in human urine.
- To characterize the activity and properties of urinary ACE.
- To compare urinary ACE with lung ACE.
Main Methods:
- Measurement of mean daily urinary ACE activity in healthy individuals.
- Correlation analysis between urinary ACE activity and urinary sodium concentration.
- Partial purification of urinary ACE using Sephadex G-200 gel filtration.
- Enzymatic characterization including pH optimum, KM, Cl- dependency, and inhibition studies.
Main Results:
- Angiotensin I-converting enzyme (ACE) was detected in normal human urine.
- Mean urinary ACE activity was 0.38 +/- 0.04 units/day.
- Urinary ACE activity showed a significant positive correlation with excreted sodium levels (r = 0.76, p < 0.005).
- Partial purification revealed three distinct molecular weight forms of urinary ACE (>400,000, 290,000, and 140,000 Da).
- These urinary ACE forms exhibited identical enzymatic properties to human lung ACE.
Conclusions:
- Angiotensin I-converting enzyme (ACE) is present and active in human urine.
- Urinary ACE excretion is linked to sodium balance.
- The biochemical properties of urinary ACE are consistent with those of lung ACE, indicating a potential common origin or similar functional role.