Hydrolysis of Casein-Derived Peptides α S1 -Casein(f1-9) and β-Casein(f193-209) by Lactobacillus helveticus Peptidase Deletion Mutants Indicates the Presence of a Previously Undetected Endopeptidase

Abstract
Peptides derived from hydrolysis of α S1 -casein(f1-9) [α S1 -CN(f1-9)] and β-CN(f193-209) with cell extracts of Lactobacillus helveticus CNRZ32 and single-peptidase mutants (Δ pepC , Δ pepE , Δ pepN , Δ pepO , and Δ pepX ) were isolated by using reverse-phase high-performance liquid chromatography and were characterized by mass spectrometry. The peptides identified suggest that there was activity of an endopeptidase, distinct from previously identified endopeptidases (PepE and PepO), with specificity for peptide bonds C terminal to Pro residues. Identification of hydrolysis products derived from a carboxyl-blocked form of β-CN(f193-209) confirmed that the peptides were derived from the activity of an endopeptidase.

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