Abstract: The casein of the milk of bactrian camels in Xinjiang was hydrolyzed with pepsin and/or trypsin, and the angiotensin converting enzyme (ACE) inhibitory activity of the resulting hydrolysates was determined by measuring the production of hippuric acid (HA) by reversed-phase high performance liquid chromatography (RP-HPLC) using an external standard method. The competitive relationship between the casein hydrolysates and captopril was investigated by using the Michaelis-Menten equation. The ACE inhibitory activity of the retenates obtained after ultrafiltration of the hydrolysates through membranes with molecular mass cutoff of 50, 10 and 3 kDa was determined. The results showed that the degree of hydrolysis was 3.7% after 4 h hydrolysis with trypsin compared to 16.58% with pepsin. The percentage of ACE inhibition by the 2 h hydrolysate with trysin was 74.67% as opposed to 72.33% with pepsin. When the casein was hydrolyzed sequentially with pepsin for 2 h followed by trypsin for 4 h, the degree of hydrolysis increased in a linear manner with hydrolysis time. The percentage of ACE inhibition by the hydrolysate within 2 h reached 66.27%, which did not increase with hydrolysis time. Trypsin may act on the bioactive peptides, thus reducing the enzyme activity. At increasing substrate concentration, the hydrolysate could not counteract the ACE inhibitory effect of the polypeptides, which was characteristics of non-competitive inhibitors. The inhibitory constant Ki of the polypeptides was 0.25 mg/mL. The ACE inhibitory activity of the 3–10 kDa retenate was the highest, and the peptides LLVVYPWTR and VLPVPQQMVPYPQR were found to be structurally similar to the known ACE inhibitory peptides.

Key words: Keywords: angiotensin converting enzyme, inhibitory peptide, camel milk, casein, lowering blood pressure

摘要： 对新疆双峰驼乳酪蛋白分别进行胃蛋白酶和胰蛋白酶的单酶和双酶联合水解，用反相高效液相色谱外标法，对产生的马尿酸含量进行检测，测定水解产物血管紧张素转化酶（angiotensin converting enzyme，ACE）抑制活性。通过米式方程对比水解产物与卡托普利之间的竞争关系，并用50、10、3 kDa的超滤膜对水解液进行超滤，测定截留液ACE抑制活性。结果表明：驼乳酪蛋白单酶水解12 h过程中，胰蛋白酶水解4 h，水解度达到3.7%，胃蛋白酶水解4 h，水解度达到16.58%，胰蛋白酶水解2 h，水解

关键词: 血管紧张素转化酶, 抑制肽, 驼乳, 酪蛋白, 降血压