Characterization of chymase from human vascular tissues

Area of Science:

• Biochemistry
• Vascular Biology
• Enzymology

Background:

• Angiotensin II plays a crucial role in regulating blood pressure and vascular function.
• The specific enzymes responsible for angiotensin II generation in human vascular tissues have not been fully elucidated.

Purpose of the Study:

• To identify and characterize the chymostatin-sensitive angiotensin II-generating enzyme present in human gastroepiploic arteries.
• To determine the enzymatic properties and N-terminal sequence of the purified enzyme.

Main Methods:

• Purification of the enzyme using heparin affinity and gel filtration chromatography.
• Enzyme activity assays with various substrates and inhibitors.
• Determination of molecular mass, optimal pH, and kinetic parameters (Km, Vmax, kcat).
• N-terminal amino acid sequencing.

Main Results:

• A 30 kDa enzyme was purified from human gastroepiploic arteries.
• The enzyme exhibited optimal activity between pH 7.5 and 9.0 and was inhibited by chymostatin, phenylmethylsulfonyl fluoride, and soybean trypsin inhibitor.
• The enzyme efficiently converted angiotensin I to angiotensin II but did not hydrolyze other tested peptides.
• N-terminal sequencing revealed identity to human skin/heart chymase.

Conclusions:

• The chymostatin-sensitive angiotensin II-generating enzyme in human vascular tissue is chymase.
• This finding identifies chymase as a significant enzyme in vascular angiotensin II production.
• Chymase's role in the vasculature warrants further investigation for potential therapeutic targets.