Evaluation of ACE inhibitory activity of dipeptides generated by the action of porcine muscle dipeptidyl peptidases

Dipeptidyl peptidases (DPP) constitute a group of proteolytic enzymes able to release a good number of dipeptides from the N-terminus of both synthetic substrates and natural polypeptides. Specific sequences generated by the action of DPP purified from porcine skeletal muscle have been assayed to evaluate their capacity to inhibit the activity of angiotensin-I converting enzyme (ACE; EC 3.4.15.1). A fluorimetric assay based on the hydrolysis of the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitrophenylalanylproline by the action of ACE was used for this purpose. The generated fluorescence of the product (the o-aminobenzoylglycine group) was continuously monitored in a microtiter-plate multiscan fluorometer.Among the assayed dipeptides, Arg-Pro showed the strongest ACE inhibitory activity, being able to suppress more than 60% of initial enzyme activity at a concentration of 25 μM. Dipeptides Lys-Ala, Gly-Pro and Ala-Ala also demonstrated to be effective ACE inhibitors, although at a lower degree. Dipeptides Ala-Arg and Gly-Arg caused a more moderate inhibition of ACE activity, and even lower was the inhibition exerted by Arg-Arg. From the data obtained, it is suggested that the proteolytic action of DPP along the ripening period of dry-cured meat products could contribute to the generation of antihypertensive peptides.