Antihypertensive properties of tilapia (Oreochromis spp.) frame and skin enzymatic protein hydrolysates

Figures & data

Figure 1. (a) Degree of hydrolysis (DH) of tilapia frame protein isolate (FPI) during enzymatic hydrolysis. (b) DH of tilapia skin protein isolate (SPI) during enzymatic hydrolysis.

Table 1. Degree of hydrolysis (DH), protein content and yields of tilapia frame and skin protein hydrolysates after 4-h hydrolysis.

Samples	Enzyme (E/S^a: 1%)	Degree of Hydrolysis (%)	Protein content (%)	Yield^b (%)
Frame protein hydrolysates (FPHs)	Pepsin (FPHPe)	23.46 ± 1.08^a	84.93 ± 1.01^a	80.66 ± 6.83^a
	Papain (FPHPa)	15.38 ± 0.04^c	68.88 ± 5.36^b	56.42 ± 14.03^b
	Bromelain (FPHBr)	20.01 ± 0.22^b	89.05 ± 1.10^a	67.85 ± 0.78^a
Skin protein hydrolysates (SPHs)	Pepsin (SPHPe)	6.48 ± 0.10^e	79.51 ± 8.37^a	105.14 ± 14.09^a
	Papain (SPHPa)	7.44 ± 0.20^e	81.43 ± 3.33^a	81.25 ± 17.47^a
	Bromelain (SPHBr)	10.33 ± 0.15^d	68.21 ± 2.80^b	92.39 ± 0.40^a

^aE/S: the ratio of the weights of enzymes against substrates.

^bThe yield was calculated based on the dry weight of resultant hydrolysate against the dry weight of protein isolate used for hydrolysis.

Results are presented as mean ± standard deviation with triplicate measurements. For each column, values that contain different letters are significantly different at p< 0.05.

Figure 2. SDS-PAGE of samples from tilapia frame protein isolate (FPI, lane A), frame protein hydrolysates generated by pepsin (FPHPe, lane B), papain (FPHPa, lane C) and bromelain (FPHBr, lane D), skin protein isolate (SPI, lane E), and skin protein hydrolysates generated by pepsin (SPHPe, lane F), papain (SPHPa, lane G) and bromelain (SPHBr, lane H).

Table 2. Number of predictive angiotensin converting enzyme (ACE)-inhibitory peptides released from identified tilapia (a) frame proteins and (b) skin proteins using BIOPEP’s enzyme action tool.

(a)	Alpha actin*	Myosin heavy chain^a,*	Creatine kinase^b,*	Troponin T*	Fructose-bisphosphate aldolase A*
Pepsin	13	68	16	21	11
Papain	18	61	18	15	13
Bromelain	12	38	5	5	10
Pepsin+Trypsin+ Chymotrypsin A	18	76	24	18	10
Pepsin+Trypsin+ Chymotrypsin C	22	78	27	16	11
(b)	Collagen alpha-1(I) chain^c, *	Collagen alpha-2(I) chain^d, *
Pepsin	54	51
Papain	129	121
Bromelain	97	85
Pepsin+Trypsin+ Chymotrypsin A	104	96
Pepsin+Trypsin+ Chymotrypsin C	221	214

^aMyosin heavy chain, fast skeletal muscle-like.

^bCreatine kinase M-type-like.

^cCollagen alpha-1(I) chain-like isoformX2.

^dCollagen alpha-2(I) chain-like isoformX1.

*Protein sequences of the tilapia skin proteins shown in this table were all identified in our previous study [2].

Figure 3. (a) In vitro Angiotensin-I converting enzyme (ACE) inhibitory activities of frame protein hydrolysates (FPHs: FPHPe, FPHPa, and FPHBr) and skin protein hydrolysates (SPHs: SPHPe, SPHPa, and SPHBr) generated by pepsin, papain, or bromelain. Bars with different letters are significantly different (p < 0.05). (b) The correlation plot between degree of hydrolysis (DH) and ACE inhibitory activities for FPHs (●) and SPHs (▲). The Pearson’s r value is 0.9607 and p < 0.05 represents the correlation is significant.

Figure 4. (a) In vitro angiotensin-I converting enzyme (ACE) inhibitory activities of the ultrafiltration fractions of pepsin-hydrolyzed frame protein hydrolysate (FPHPe) at of 0.6 mg/mL. (b) In vitro renin inhibitory activities of the fractions from FPHPe at of 1 mg/mL. Bars with different letters have significantly (p < 0.05) different mean values.

Figure 5. The effect of the < 1 kDa ultrafiltration fraction from pepsin-hydrolyzed frame protein hydrolysate (FPHPe1) on (a) systolic blood pressure (SBP), (b) diastolic blood pressure (DBP), (c) mean arterial pressure (MAP), and (d) heart rate (HR) of spontaneously hypertensive rats (SHRs) after oral gavage. Different letters above the bars indicate significant differences (p < 0.05).

Huang -B-B, Lin H-C, Chang Y-W. Analysis of proteins and potential bioactive peptides from tilapia (Oreochromis spp.) processing co-products using proteomic techniques coupled with BIOPEP database. J Funct Foods. 2015;19: Part A:629–11.

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