Purification and characterization of an epsilon-poly-L-lysine-degrading enzyme from an epsilon-poly-L-lysine-producing strain of Streptomyces albulus

Abstract

An epsilon-poly-L-lysine-degrading enzyme of an epsilon-poly-L-lysine-producing strain of Streptomyces albulus was purified and characterized. The enzyme was tightly bound to the cell membrane. After solubilization with NaSCN, the enzyme was purified to homogeneity by phenyl-Sepharose CL-4B column chromatography. The subunit molecular mass of the purified enzyme was 54 kDa. Enzyme activity was inhibited by o-phenanthroline, and could be restored in the presence of 1 mM Mg(2+), Ca(2+), Fe(3+) or Zn(2+). The mode of epsilon-poly-L-lysine degradation was of the exo-type, and the enzyme released N-terminal L-lysines one by one. The enzyme acted on various peptides possessing L-lysine residues at the N-terminus and was classified as an aminopeptidase. Epsilon-Poly-L-lysine-degrading activity was found in the membrane fraction of some other Streptomyces strains as well as that of Streptomyces albulus. Streptomyces virginiae IFO 12827 and Streptomyces norsei IFO 15452 exhibited high epsilon-poly-L-lysine-degrading activity, and both strains could produce epsilon-poly-L-lysine, indicating a correlation between the distribution of membrane-bound epsilon-poly-L-lysine-degrading enzyme and epsilon-poly-L-lysine-producing activity.