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BACKGROUND: Angiotensin I-converting enzyme (ACE) is a dipeptidyl carboxypeptidase associated with the regulation of blood pressure. ACE inhibition results in a lowering of blood pressure. Lactic acid bacteria are known to produce ACE inhibitors during fermentation. Fermented camel milk is the main traditionally fermented dairy food for desert nomads. The beneficial effects of fermented camel milk, which include the prevention of such diseases and conditions as gastroenteritis, tuberculosis and hypertension, have been demonstrated experimentally.

RESULTS: ACE inhibitory activity was observed in fermented milk containing Lactobacillus helveticus 130B4, a strain isolated from traditionally fermented camel milk. The peptide that inhibited ACE was purified from the fermented milk by reverse-phase high-performance liquid chromatography. The amino acid sequence of the peptide was identified as Ala-Ile-Pro-Pro-Lys-Lys-Asn-Gln-Asp (IC(50) = 19.9 mu mol L(-1)). The same Ala-Ile-Pro-Pro-Lys-Lys-Asn-Gln-Asp sequence was found in kappa-casein (kappa-CN) f107-115 from milk. The inhibitory activity of this nonapeptide (kappa-CN f107-115) was almost preserved even after successive digestion with pepsin, trypsin and chymotrypsin. Furthermore, the inhibitory activity of the purified peptide was completely preserved after heat treatment at 100 degrees C for 20 min.

CONCLUSION: The fermented milk prepared with Lactobacillus helveticus 130B4 contained an ACE inhibitory peptide, kappa-CN 107-115. This fermented milk was expected to have anti-hypertensive effect after ingestion because the peptide was stable to digestive protease and heat treatment in vitro. (c) 2008 Society of Chemical Industry