PURIFICATION AND CHARACTERIZATION OF AN X-PROLYL DIPEPTIDYL AMINOPEPTIDASE FROM LACTOBACILLUS-HELVETICUS LHE-511

An X- prolyl dipeptidyl aminopeptidase from cells of Lactobacillus hel veticus LHE-511 was purified by 3 steps of column chromatography and c haracterized. The purified enzyme selectively hydrolyzed peptides and pNA derivatives containing proline at the penultimate position. The mo lecular mass of the enzyme was estimated to be 93 kDa by gel filtratio n and 87 kDa by SDS-PAGE, and it appeared to exist as a monomer. The o ptimal pH and temperature for activity were 6.5 and 50-degrees-C, resp ectively. The enzyme was weakly activated by Zn2+, Fe2+ or Mg2+ ions a nd strongly inhibited by Cu2+ or Hg2+ ions. Moreover, it was strongly inhibited by inhibitors of serine proteases (diisopropylfluorophosphat e, phenylmethylsulfonylfluoride) and sulfhydryl group-blocking reagent s (p-chloromercuribenzoic acid).