Karakterisasi Peptida Inhibitor Angiotensin Converting Enzyme (ACE) Hidrolisat Daging Kambing Kacang (Capra aegagrus hircus Linn) dalam Potensinya sebagai Ingredien Pangan Fungsional

Abstract

The kacang goat (Capra aegagrus hircus) is indigenous to Indonesia and Malaysia, and is common throughout in Southeast Asia. The negative issue facing Indonesian people is that consumption of goat meat can lead to hypertension. Natural angiotensin converting enzyme (ACE) inhibitory peptides from animal protein are considered as an alternative antihypertensive agent. ACE inhibitory peptide could be generated by hydrolysis the protein sources by using the proteolytic enzymes. The purpose of this research was to obtain the water soluble fraction of protein hydrolysates derived from kacang goat in their inhibition of ACE and antihypertensive activities. This study used ten male of kacang goats aged 8-24 months from a local farm in East Java were brought to Bogor by Mitra Tani Farm, West Java Indonesia. The goats divided into two slaughter ages, namely < 1.5 years old and >1.5 years old. Kacang goats are generally slaughtered for consumption at these ages. The body part used for this research was the carcass leg. The contents of protein, fat, moisture, ash, and amino acid in the goat meat were not different on both of slaughter ages. The dominant amino acids found in the goat meat were glutamic acid, aspartic acid, leucyne and lysine. Protein hydrolysate of kacang goat meat was generated by adding endoprotease into homogenate (minced meat to distilled water, 1:3) with several concentrations (0.5%, 1.0%, 1.5% w/w of the total substrate) and hydrolyzed for 60 min. The next hydrolysis was conducted by adding protease complex at several concentrations (0.5%, 1.0%, 1.5% w/w of the total substrate) to the first hydrolysate. Digestion proceeded for 1, 3, and 5 h. The pH of homogenate was kept constant by addition of 6 N NaOH and was monitored every 30 min during hydrolysis. The water soluble fraction (WSF) of hydrolysate was obtained by separating the supernatant and its residue. The crude hydrolysates were charactherized by analysis the ACE inhibitory activity, degree of hydrolysis, soluble protein content, peptide content and yield percentage. The ACE inhibitory activity of crude hydrolysate at 0.5 mg/mL and 1.0 mg/mL ranged between 21.2-45.2% and 48-58%, respectively. The crude hydrolysates had degree of hydrolysis ranged between 10.4-26.3%, soluble protein contents ranged between 534.7 - 579.9 mg/g, peptide contents 400.4-520.8 mg/g and the yield percentage ranged between 49.9-76.0%. The highest ACE inhibitory activity resulted from a hydrolysate digested for 4 h with 5 g kg-1 of both enzymes. The hydrolysate was further fractionated gradually to determine the sequence of ACE inhibitory peptide. Fractionation of protein hydrolysate was started by concentrating the hydrolysate through ultrafiltration system by using centrifugal filter membrane (molecular weight cut-off, MWCO; 3 kDa). Furthermore, an active fraction was separated on a Sephadex G-10 column. The most active fraction was then purified by high performance liquid chromatography- reversed phase (HPLC-RP) gradually with two different types of columns and was obtained an ACE inhibitory peptide with a molecular weight of 478 Da. The ACE inhibitory peptide from most active fraction with IC50 : 12.91 mg/mL (27.0 μM) was identified as tetra-peptide, Phe-Gln-Pro-Ser. Protein hydrolysate and Phe-Gln-Pro-Ser demonstrated the potent antihypertensive activities in spontaneous hypertensive rats. The reduction in systolic blood pressure (SBP) was 19.3±1.66 mm Hg at 6 h after administration 10 mg hydrolysate per kg of body weight (P < 0.01) and 10.57±1.58 mm Hg at 8 h after oral administration of 2.39 mg Phe-Gln-Pro-Ser per kg of body weight (P < 0.01). The Phe-Gln-Pro, as a reference ACE inhibitory peptide, could decrease SBP was 12.6 ± 2.54 mm Hg after 6 h orally administration. Protein hydrolysate of kacang goat meat showed a great potency as active ingredient in hydrolysate-based beverages model.