Biosynthesis of ε-poly-l-lysine in a cell-free system of Streptomyces albulus

ε-Poly-l-lysine (ε-PL) is a homo-poly-amino acid characterized by a peptide bond between carboxyl and ε-amino groups of l-lysine. Here we report the cell-free synthesis of ε-PL by a sensitive radioisotopic ε-PL assay system. In vitro ε-PL synthesis depended on ATP and was not affected by ribonuclease, kanamycin, or chloramphenicol. ε-PL synthesizing activity was detected in the membrane fraction. The reaction product, ε-PL, from l-lysine was identified by MALDI-TOF MS and the number of lysine residues of the ε-PL products was apparently 11–34. These results suggest that the biosynthesis of ε-PL is nonribosomal peptide synthesis and is catalyzed by membrane bound enzyme(s). The enzyme preparation showing the ε-PL synthesizing activity also catalyzed lysine-dependent AMP production and an ATP-PPi exchange reaction, suggesting that l-lysine is adenylated in the first step of ε-PL biosynthesis.