Isolation, Purification And Identification Of Angiotensin I-converting Enzyme Inhibitory Peptides From Koumiss, A Traditional Fermented Mare's Milk

Chemical and microbiological compositions of the sample of traditional fermented mare's milk in Xilinguole were determined. Meanwhile, about angiotensin I-converting enzyme inhibitory peptides from koumiss were analyzed.The average contents of fat, protein, lactose and ash were1.97±0.43,2.16±0.48,2.58±0.41,0.30±0.06 g/100g respectively,titration acidity was 98.63±3.25 oT, vitamin C was 10.55±0.24 mg/100g, The average contents of Ca, P were 78.49±1.55,55.63±0.69 mg/100g,on average, lactic acid content was 0.85±0.04g/100g and ethanol content was 1.31±0.08 g/100g.The counts of lactic acid bacteria were 7.86±0.86 log cfu/mL ,the counts of yeast were 6.48±0.71 log cfu/mL,MPN﹤30。Angiotensin I-converting enzyme (ACE) inhibitory activities in untreated koumiss and koumiss digested with ACE, pepsin, trypsinase and chymotrypsin were compared and analyzed. Four novel ACE inhibitory peptides (PI, PK, PM and PP) were purified using ultrafiltration and high performance liquid chromatography (HPLC). The classification study showed that these four peptides were of the true inhibitor type. The amino acid sequences of these peptides are YQDPRLGPTGELDPATQPIVAVHNPVIV, PKDLREN, LLLAHLL and NHRNRMMDHVH, respectively. Their individual IC50 (50% inhibitory concentration)values are as follows: 14.53±0.21μM, 9.82±0.37μM, 5.19±0.18μM and 13.42±0.17μM. From sequence analysis, we determined that PI was part ofβ-casein in mare's milk. The three peptides PK, PM and PP did not correspond with any known milk protein. The results suggest that koumiss is rich in ACE inhibitory peptides, and the ACE inhibitors in koumiss are of the pro-drug type or a mixture of the pro-drug type and the true inhibitor type.These results may provide evidence about the beneficial effects of koumiss, especially on cardiovascular health.