Purification and characterization of an endopeptidase that has an important role in the carboxyl terminal processing of antihypertensive peptides in Lactobacillus helveticus CM4

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AimsTo purify and characterize a peptidase that can catalyse C-terminal processing of antihypertensive peptide from Lactobacillus helveticus CM4.Methods and ResultsAn endopeptidase which seems to process the carboxyl terminal end of two antihypertensive peptides, Val-Pro-Pro and Ile-Pro-Pro, was purified from Lactobacillus helveticus CM4 by four stages of column chromatography, using synthetic pro-peptide as a substrate. The molecular weight of the purified enzyme was estimated to be 67 000 by SEPHACRYL S-200 and 70 000 by SDS-PAGE analysis. The purified enzyme generated: (i) Val-Pro-Pro from Val-Pro-Pro-Phe-Leu and Val-Pro-Pro-Phe-Leu-Gln-Pro, and (ii) Ile-Pro-Pro from Ile-Pro-Pro-Leu-Thr and Ile-Pro-Pro-Leu-Thr-Gln-Thr, but theses peptides could not be generated from Val-Pro-Pro-Phe, Val-Pro-Pro-Phe-Leu-Gln, Ile-Pro-Pro-Leu and Ile-Pro-Pro-Leu-Thr-Gln. Part of the amino terminal sequence of the purified enzyme had homology to a previously reported pepO gene product.ConclusionThese results suggest that the purified endopeptidase isolated in this study have an important role in the carboxyl terminal processing of two antihypertensive peptides in Lact. helveticus CM4.

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