Biochemistry and Enzymology of Poly-Epsilon-l-Lysine Degradation

Abstract

Poly-ε-l-lysine (ε-poly-l-lysine, ε-PL) is used as a food additive on the basis of its strong antimicrobial activity (Fine chem 29:18–25, 2000). ε-PL is industrially produced by fermentation process using Streptomyces albulus. Recently, the biosynthetic mechanism (Nat Chem Biol 4:766–772, 2008) and microbial degradation of ε-PL (FEMS Microbiol Lett 207:147–151, 2002; Arch Microbiol 178:325–330, 2002; J Biosci Bioeng 96:92–94, 2003; Appl Microbiol Biotechnol 72:173–181, 2006) have been reported. The ε-PL-degrading activity is detected in ε-PL-tolerant bacteria, indicating the contribution of ε-PL-degrading activity to bacterial growth in the presence of ε-PL. The purified ε-PL-degrading enzymes catalyze the endo- and/or exo-type degradation of ε-PL (FEMS Microbiol Lett 207:147–151, 2002; J Biosci Bioeng 96:92–94, 2003). Various peptides and proteins serve as substrates for the ε-PL-degrading enzymes. Probably, the adventitious possession of proteases, exhibiting high ε-PL-degrading activity, enables ε-PL-tolerant bacteria to grow well even in the presence of ε-PL. ε-PL-producing Streptomyces strains also possess high ε-PL-degrading activity in their membrane fraction (Arch Microbiol 178:325–330, 2002). ε-PL-degrading enzyme purified from S. albulus is characterized as a zinc-containing aminopeptidase. In Streptomyces strains, the correlative distribution of ε-PL-degrading activity and ε-PL-producing activity is observed, suggesting that the ε-PL-degrading activity is localized in the cell membrane of ε-PL producers for self-protection against ε-PL.