Purification and characterization of CEP from Lactococcus lactis ssp. lactis

The cell-envelope proteinase (CEP) of Lactococcus lactis ssp. lactis LB12 was released from cells by treatment with lysozyme, purified by ammonium sulfate precipitation and chromatographed on DEAE-Sephadex A-25 and Sephacryl S-300 HR. The purified CEP is a monomer structure and has molecular mass of about 53 kDa. Optimal activity occurred at pH 7.5 and 40 °C. It is a metallopeptidase, activated by Mn²⁺, Mg²⁺, Ca²⁺, inhibited by Co²⁺, Zn²⁺, Ni²⁺ and EDTA, and a serine proteinase which is inhibited by PMSF. The sequence of the first 13 amino acids of the N-terminal of the CEP was determined to be Asp-Val-Phe-Ala-Pro-His-Met-Ala-Asn-Val-Ala-Ala-Val, and the whey protein hydrolysate produced by the CEP displayed ACE-inhibitory activity.