Intracellular X‐prolyl dipeptidyl peptidase from <i>Lactococcus lactis</i> spp. <i>lactis</i> : purification and properties

Abstract

An X‐prolyl dipeptidyl peptidase (EC 3.4.14.5) has been purified from a crude intracellular extract from Lactococcus lactis spp. lactis NCDO 763 by ion‐exchange chromatography and gel filtration. One protein band was detected after electrophoresis of the purified enzyme in the presence or absence of sodium dodecyl sulphate. The enzyme is a 190 kDa dimer composed of identical subunits. Optimal activity occurs at pH 8.5 and 40–45°C and the enzyme is inhibited by reagents specific for serine proteases, such as diisopropylfluorophosphate. The enzyme hydrolyzes p ‐nitroanilide‐ or β‐naphthylamide‐substituted X‐Pro dipeptides, as well as β‐casomorphin.