Occurrence, biosynthesis, biodegradation, and industrial and medical applications of a naturally occurring ε-poly-L-lysine.

ε-Poly-L-lysine (ε-PL) consists of 25-35 L-lysine residues with linkages between the α-carboxyl groups and the ε-amino groups. It exhibits antimicrobial activity against a spectrum of microorganisms, including bacteria and fungi. Because of its high levels of safety and biodegradability, it is used as a food preservative in several countries. We recently identified an ε-PL synthetase (Pls) as a membrane protein, and investigated the catalytic mechanism. Pls was found to be an unusual non-ribosomal peptide synthetase (NRPS)-like peptide synthetase producing ε-PL with chain-length diversity. In addition, 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 ε-PL fermentation are necessary for the accumulation of intracellular ATP, rather than inhibition of the ε-PL-degrading enzyme.