Angiotensin I conversion by human and rat chymotryptic proteinases

Area of Science:

• Biochemistry
• Enzymology
• Physiology

Background:

• Serine proteinases are enzymes with similar sizes and specificity for aromatic residues.
• These enzymes play roles in biological processes, including the generation of angiotensin II.

Purpose of the Study:

• To compare the angiotensin I converting activity of human skin chymotrypsin-like proteinase, human neutrophil cathepsin G, rat mast cell chymase, and rat salivary gland tonin.
• To investigate the substrate specificities and potential physiological significance of these enzymes.

Main Methods:

• Enzymes were tested for their ability to convert angiotensin I to angiotensin II using synthetic substrates.
• Kinetic constants (Km and Kcat) were determined for human skin enzyme.
• Immunologic characterization was performed using monospecific antisera.

Main Results:

• Human skin proteinase, cathepsin G, and tonin efficiently converted angiotensin I to angiotensin II.
• Chymase showed lower activity due to preferential cleavage at a different site.
• Human skin proteinase exhibited kinetic constants comparable to or exceeding angiotensin-converting enzyme.

Conclusions:

• Human skin proteinase, cathepsin G, and tonin represent distinct pathways for tissue angiotensin II generation.
• The activity of human skin proteinase suggests a significant physiological role in regulating tissue microenvironment processes.
• These enzymes may be crucial in various biological regulatory mechanisms.