Physiological function analysis of ε-poly-L-lysine-degrading enzymes in Streptomyces albulus

Abstract:

[Objective] The distribution and physiological function of ε-poly-L-lysine-degrading enzyme (Pld) in Streptomyces albulus were investigated in this study. [Methods] The sequence of Pld in the reported ε-poly-L-lysine (ε-PL) producing strains were mined and analyzed from their genome by bioinformatics methods, and then two types of Plds in S. albulus M-Z18 genome were knocked out, complemented and overexpressed by genetic methods, those recombinant strains were used to study the degradation of ε-PL, the minimum inhibitory concentration (MIC) of ε-PL and their ε-PL productions. [Results] pldⅠ and pldⅡ are widely distributed in S. albulus, and their protein sequences are highly conserved. The results showed that PldⅠ and PldⅡ in the S. albulus M-Z18 all could degrade ε-PL. However, the degradation activity of PldⅡ was dominant, while PldⅠ and PldⅡ had a synergistic effect on the degradation of ε-PL. The MIC values of recombinant strains with pldⅠ or/and pldⅡ overexpression toward ε-PL were significantly increased, especially the MIC value of pldⅠ and pldⅡ co-overexpressed strain was 2.19 folds higher than that of the original strain. Surprisingly, these recombinant strains showed no significant difference in the production of ε-PL at pH 3.0-5.5 compared with the original strain. [Conclusion] PldⅠ and PldⅡ are highly conserved in S. albulus, which physiological functions are protect S. albulus from the inhibition of its metabolite ε-PL by degradation at the neutral pH.