The cleavage of the Met-Lys bond in a bradykinin derivative by glandular kallikreins.

The research article is about a study on the cleavage of a specific bond in a bradykinin derivative by two enzymes, horse urinary and porcine pancreatic kallikreins. Various methods of making the bradykinin derivative resistant to the action of the enzymes were explored.

Enzyme Activity on the Synthetic Tridecapeptide

The article first presents a model substrate, the synthetic tridecapeptide Gly-Leu-Met-Lys-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg, for testing the action of the two enzymes, horse urinary and porcine pancreatic kallikreins.

• The Met-Lys bond in this peptide was selectively hydrolyzed by both enzymes. Hydrolyzation breaks down a compound by chemical reaction with water.

Resistance to Enzyme Activity

The researchers then explored methods of making the synthetic peptide resistant to the action of the two enzymes.

• Oxidation of the methionine residue to sulfoxide made the peptide resistant to the kallikreins. In this context, resistance means that the enzymes did not break down the peptide.
• Substitution of the methionine or lysine residues by norleucine led to peptides in which the newly created bonds were susceptible to the urinary kallikrein. This can be seen as a sensitivity test.

Inhibition of Enzyme Activity

The study also investigated methods of inhibiting the activities of the enzymes.

• Using phenylmethanesulfonyl fluoride resulted in similar inhibition of both the esterolytic and Met-Lys bond-splitting activities of both enzymes.
• The researchers found that the chloromethane derivative Ala-Leu-Lys-CH2Cl also inhibited both enzymatic activities.
• Another inhibitor tested was benzamidine. It prevented the hydrolysis of the Met-Lys bond by both kallikreins.

In all these discussions, the term “enzyme activity” refers to the ability of the enzymes to break down the peptides, specifically at the Met-Lys bond. The studied methods of resistance and inhibition are potential ways of controlling the enzyme activity. It provides insights into the enzymes’ functions and characteristics, leading to further biochemical understanding of these enzymes and the potential manipulation of their activities for various applications.