Mechanism of epsilon-poly-L-lysine production and accumulation revealed by identification and analysis of an epsilon-poly-L-lysine-degrading enzyme.

Epsilon-poly-L-lysine (epsilon-PL) is produced by Streptomyces albulus NBRC14147 as a secondary metabolite and can be detected only when the fermentation broth has an acidic pH during the stationary growth phase. Since strain NBRC14147 produces epsilon-PL-degrading enzymes, the original chain length of the epsilon-PL polymer product synthesized by epsilon-PL synthetase (Pls) is unclear. Here, we report on the identification of the gene encoding the epsilon-PL-degrading enzyme (PldII), which plays a central role in epsilon-PL degradation in this strain. A knockout mutant of the pldII gene was found to produce an epsilon-PL of unchanged polymer chain length, demonstrating that the length is not determined by epsilon-PL-degrading enzymes but rather by Pls itself and that the 25 to 35 L-lysine residues of epsilon-PL represent the original chain length of the polymer product synthesized by Pls in vivo. Transcriptional analysis of pls and a kinetic study of Pls further suggested that the Pls catalytic function is regulated by intracellular ATP, high levels of which are required for full enzymatic activity. Furthermore, it was found that acidic pH conditions during epsilon-PL fermentation, rather than the inhibition of the epsilon-PL-degrading enzyme, are necessary for the accumulation of intracellular ATP.