Preparation Of Polypeptides From Goat Brain Protein And Antioxidant Activities

In order to explore goat brain functional polypeptide and goat brain functional food, the goat brain protein poweder defatted by petroleum etherv was used as the experiment material to prepare antioxidant peptides. The protein content and the amino acids composition of the defatted goat brain poweder were determined;The enzymatic hydrolysis parameters of defatted goat brain protein with Bacillus subtilis neutral protease were optimized by response surface methodology; The relationship between antioxidant activity and degree of hydrolysis contorlled by the time of hydrolysis was studied; In addition, the molecular mass distribution of the protein hydrolysates hydrolyzed by neutral protease from bacillus subtilis at different time was analysised by SDS-polyacrylamide gel electrophoresis(SDS-PAGE); The goat brain protein hydrolysates were separated and purified by Sephadex G-25 gel filtration chromatography and Sephadex G-15 gel filtration chromatography, the antioxidant properties of the protein hydrolysates were investigated in vitro. The results as follow:(1) The protein content of the defatted goat brain is 60.55%. The analysis of amino acids composition shows goat brain is rich of seven kinds of essential amino acids at least, the content of glutamic acid and aspartic acid are the highest.(2) The result of response surface methodology indicated that the optimal hydrolysis conditions were 39.4 ℃, 3.03 g/100 mL and 5653.20 U/g for temperature, concentration of substrate and enzyme/substrate ratio, respectively. The maximum predicted degree of hydrolysis under the optimal conditions was 14.79% by the time of 4h.(3) The relationship between antioxidant activity and degree of hydrolysis was found that the hydrolysates hydrolyzed by neutral protease the for 3 hour showed the strongest antioxidant activity, meanwhile the IC50 of scavenging DPPH, free radical hydroxyl, superoxide anion and nitrite were 2.49, 3.13, 10.37 and 10.89mg/mL respectively and the the IC50 of chelating Fe2+ ions was 7.48 mg/mL.(4) Goat protein contains so much protein at different molecular mass; The molecular mass of protein range from 25 KDa to 130 KDa and the molecular mass of the hydrolysates is below 10 kDa.(5) After purified by Sephadex G-25 gel filtration chromatography and Sephadex G-15 gel filtration chromatography, the obtained F4-2 fraction exhibits the strongest antioxidant activity; The IC50 of the F4-2 fraction scavenging DPPH, hydroxyl radical, superoxide anion radical, and nitrite radical is 1.64, 2.48, 7.98 and 5.14mg/mL respectively.