Kinetics of Renin and Angiotensin Converting Enzyme Inhibition by African Giant Land Snail (Archachatina marginata) Protein Hydrolysate and Membrane Ultrafiltration Peptide Fractions

The aim of the study was to produce potential antihypertensive peptides with multi-enzyme inhibitory effects from defatted snail protein meal (SnPM). The SnPM was enzymatically hydrolysed by sequential pepsin and pancreatin addition to mimic gastrointestinal tract digestion. After the digestion, approximately 81% of the initial SnPM protein was converted into soluble peptides, which were collected as the snail protein hydrolysate (SnPH). The SnPH was then fractionated using ultrafiltration membranes to obtain peptide fractions with <1, 1-3, 3-5, 5-10 and >10 kDa molecular weight sizes. The SnPH and fractionated peptides were investigated for in vitro inhibitions of angiotensin I-converting enzyme (ACE) and renin activities followed by determination of enzyme inhibition kinetics parameters.The SnPH had 68 and 59% in vitro inhibition of ACE and renin activities, respectively in comparison to the membrane fractions with 46-78 and 41-66% values. The ACE-inhibitory IC50 values were 0.22-0.79 mg/mL when compared to 0.41-0.96 mg/mL for renin, which suggests that the peptides have higher potency against ACE. The SnPH and membrane fractions inhibited ACE activity through mainly a non-competitive mechanism whereas renin inhibition was of the mixed-type. The results suggest that the snail peptides bind mainly to ACE non-active sites but could bind to both the active and non-active sites of renin.