Purification and Characterization of an Aminopeptidase from Lactobacillus delbrueckii subsp, buigaricus

An aminopeptidase was purified from cell-free extracts of Lactobacillus delbrueckii subsp, bulgaricus Bl4. Electrophoretic purity was achieved by anion exchange chromatography, metal chelating chromatography with immobilized Cu2+, and two steps of FPLC anion exchange chromatography. A molecular mass of 95 kDa was calculated by sodium dodecylsulphatepolyacrylamide gel electrophoresis (SDS-PAGE). The enzyme probably does not consist of subunits. Suitable substrates for activity assays were L-Lys-NA and L-Ala-L-Arg-NA which were cleaved fastest at 50 degrees C and pH 7. The peptidase is a metal-dependent enzyme which was inhibited completely by 0 1 mM EDTA. Activity was increased by I mM Mn2+ and O. 1 mM Hg2+. Aminopeptidase activity inhibited by EDTA could be restored by the addition of Mn2+ Properties of the enzyme are compared to the corresponding enzymes of other species of lactic acid bacteria.