Study On The Angiotensin Ⅰ-Converting Enzyme Inhibitory Peptides From Enzymatic Hydrolyzed Freshwater Fish

Enzymatic hydrolysis parameters, Angiotensin- I Converting Enzyme (ACE) inhibitory activity of hydrolysates and optimal hydrolysis condition of Flavorzyme of freshwater fishes were studied in the present paper. Molcular weight distribution and the ACE inhibitory activity of each fraction were measured, separation and structure of some fractions was also analyzed on LC-MS. Research results are as follows:1. Pretreatment affected the hydrolysis of Silver carp. Muscle treated by heating resulted in lower degree of hydrolysis (DH) and recovery ratio of nitrogen than that of fresh or frozen one, while the effects of the frozen muscle was close or better than the fresh one.2. Enzymatic hydrolysis parameters were studied. The optimum temperature for As 1.398, Flavorzyme, Alcalase and Protamex were: 40℃, 50℃, 55℃, 50℃. Optimum pH were 7.5, 7.0, 7.5, 6.5, respectively. The 12h-hydrolysate by Flavorzyme, which was bitterless , had a higher DH and ACE inhibitory activity than that of other 3 kinds of enzyme.3. Orthogonal experiment was used to study the effect of temperature, enzyme concentration, ratio of fish muscle to water and pH on DH, recovery ratio of nitrogen and ACE inhibitory activity of hydrolysates. The results showed that the optimum conditions to produce ACE inhibitory peptides was: temperature 50C, enzyme concentration 5000u/g.pr, ratio of fish muscle to water 1 .' 6, pH 8.0, and ACE inhibitory activity was 70%, DH and recovery ratio of nitrogen was 34% and 92%.4. The ACE inhibitory effects of the hydrolysates derived from different freshwater fish and different part was researched. For different fish, the inhibitory ability was: Bream >Grass carp >Silver carp, Bighead>Common carp, Crucian carp. For different part was: white muscle>mixed muscle>skin, red muscle>abdomen.5. Molecular weight distribution and the ACE inhibitory activity were measured. The hydrolysates of Silver carp were separated by Sephadex G-15 after different hours of enzymatic treatments. They appeared eight fractions, among them, the four fractions ahead had ACE inhibitory activity, but the four behind had no ACE inhibitory activity. The Molecular weight of fraction I was more than 1500 Da, fraction II -VIII was between 700 Da. and 100 Da. The proportion of fraction I decreased quickly with time prolonging, while the sum of fraction V ~W1 increased. The sum of fraction II -IV almost not changed, it kept at 55%. LC-MS analyzing showed that Fraction III-V were composed of many peptides, rather than a pure substance.