Tonin, an esteroprotease from rat submaxillary glands

Area of Science:

• Biochemistry
• Enzymology
• Physiology

Background:

• Tonin is an enzyme identified in rat submaxillary glands.
• It plays a role in the renin-angiotensin system by processing angiotensinogen.

Purpose of the Study:

• To characterize the enzymatic properties and substrate specificity of tonin.
• To determine the classification and inhibitory profile of tonin.

Main Methods:

• Enzyme activity assays using synthetic substrates (e.g., benzoyl-arginine esters).
• Determination of optimal pH for tonin activity.
• Inhibition studies using various protease inhibitors (e.g., DFP, PMSF, STI, aprotinin).

Main Results:

• Tonin liberates angiotensin II from angiotensinogen and angiotensin I.
• It hydrolyzes various arginine-containing synthetic substrates optimally at pH 9.0.
• Tonin demonstrates high specificity towards angiotensin I.
• The enzyme is inhibited by serine protease inhibitors like DFP, PMSF, soybean trypsin inhibitor, and aprotinin.

Conclusions:

• Tonin is classified as a serine protease with trypsin- and chymotrypsin-like esteroprotease activity.
• It belongs to the same enzyme family as glandular kallikrein and NGF gamma subunit.
• Tonin's specific activity and inhibition profile provide insights into its physiological role.