PREPARATION OF BACTERIAL X-PROLYL DIPEPTIDYL AMINOPEPTIDASE AND ITS STABILIZATION BY ORGANIC COSOLVENTS

To obtain large amounts of the X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis subsp lactis (PepX, E.C. 3.4.14.5), PepX was purif ied from a commercial L. lactis cell extract. The enzyme was purified in only three steps and the last one was performed by HPLC on a C-4 re verse-phase column using acetonitrile as an eluent. Despite its high m olecular mass (175 kDa), the enzyme was recovered with a good activity yield (75%). Advantages and drawbacks of this technique compared to t he classical ones are discussed. The stability of the enzyme in aqueou s solutions and in the presence of 10 water-miscible solvents was also investigated. PepX was found to be stabilized by dimethyl sulfoxide, triglyme, and glycerol. (C) 1995 Academic Press, Inc.