PURIFICATION, CRYSTALLIZATION, AND PRELIMINARY-X-RAY ANALYSIS OF PEPX, AN X-PROLYL DIPEPTIDYL AMINOPEPTIDASE FROM LACTOCOCCUS-LACTIS

The X-prolyl dipeptidyl aminopeptidase PepX, a serine peptidase isolat ed originally from Lactococcus lactis subsp lactis NCDO 763, was clone d and overproduced in Escherichia coli. The enzyme was isolated in its active form in two purification steps. Crystals of PepX were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at pH 5.0. The crystals are orthorhombic with cell dim ensions a=92.8 Angstrom, b = 102.6 Angstrom, and c=101.6 Angstrom, spa ce group P2(1)2(1)2, and probably contain one monomer of 87.5 kDa in t he asymmetric unit. The crystals, very stable under X-rays, diffract t o at least 2.2 Angstrom and are suitable for high-resolution structura l analysis. (C) 1995 Wiley-Liss, Inc.