Abstract
X-prolyl-dipeptidyl-aminopeptidases were purified from cell-free extracts of Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus acidophilus by anion exchange chromatography, metal chelating chromatography with immobilized Zn2+ and FPLC anion exchange chromatography. The enzymes displayed very similar properties. A single band with a molecular mass of about 95 kd appeared in SDS-PAGE. By gel filtration it was shown that the native enzymes are dimeric. The enzymes belong to the group of serine enzymes since they were strongly inhibited by diisopropyl fluorophosphate (1 mm). Highest activity was observed at 45°C and pH 6·5, respectively. Enzyme activities were not affected by 1 mm EDTA, Ca2+, Mg2+, Co2+, or 1–10 mm β-mercaptoethanol, but were inhibited by 1 mm Cu2+, Zn2+ or Hg2+. The purified enzymes are compared with X-prolyl-dipeptidyl-aminopeptidases from other lactic acid bacteria.
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