Bioactive peptides showing Angiotensin-I-Converting Enzyme inhibitory (ACEi) activity can control blood pressure. They can be produced from various protein sources, including fish gelatin. This article provides a systematic review and meta-analysis on gelatin extraction, conditions of enzymatic hydrolysis, characteristics of ACEi peptides, and effect of hydrolysis procedure on ACEi peptides. Fish gelatin preparation uses various solutions such as acids, bases and distilled water. Enzymatic hydrolysis is carried out with an E/S ratio of 0.2 – 7% and temperature of 28.9 oC (using bromelain) and 60.6 oC (using Alcalase). Level of pH in hydrolysis also varied greatly, from 2 (using Pepsin) to 10 (using Purafect enzyme). The molecular weight of fish gelatin ACEi peptides ranged from 186-829 Da and the sequence of peptides was dominated by hydrophobic and aliphatic amino acids. Based on a meta-analysis, hydrolysis using enzyme combination resulted in more satisfying product than a single enzyme, represented with a combined effect size value of 0.593.

A protease inhibitor is a compound that potentially could inhibit the activity of a protease or some protease enzymes. It has a significant role in fish processing to prevent quality deterioration. The study aimed to investigate the inhibitory activity of wild swamp eel (Monopterus albus) plasma fractionated with ethanol to papain enzyme. The parameters analyzed were protein content, inhibitory activity to papain enzyme, and sodium dodecyl sulphate-polyacrylamide gel electrophoresis to demonstrate the protein profile. The result showed that the amount of protein in the plasma fractionated with ethanol was decreased. The effectiveness in inhibiting papain enzyme was increased when compared to that of the crude plasma, from 65 to 128.56% per mg protein. Analysis by sodium dodecyl sulfatepolyacrylamide gel electrophoresis demonstrated that the protein complex alpha-2- macroglobulin in wild swamp eel plasma consists of two different subunits of 120 kDa and 110 kDa. This study suggested that plasma fractionated with ethanol showed inhibitory activity to papain enzyme greater than that of the crude plasma.