The poly(amino acid)s γ-poly(dl-glutamic acid) (gPGA) and ϵ-poly(l-lysine) (ePL) are known to be natural linear poly(amino acid)s secreted by Bacillus spp. and Streptomyces spp., respectively. In this study, a Streptomyces strain producing both ePL and gPGA was identified. Mass spectrometry and other analyses revealed that the gPGA is a mixture of oligomers consisting of 10–13 l-glutamic acid residues linked by isopeptide bonds. In contrast to the known Bacillus gPGA, the glutamic acid oligomers have a cyclodehydrated structure in each molecule. We previously reported that the ePL molecules secreted by the same Streptomyces strain disperse only slightly in an agar culture plate, as though they were larger molecules. This phenomenon is explicable by the observed polyion complex formation between the glutamic acid oligomers and ePLs. The glutamic acid oligomers control the ePL's dispersion, which would also affect the spatial distribution of the ePL's antimicrobial activity. Therefore, gene clustering or common use of the gene was presumed for biosynthesis of the two poly(amino acid)s. However, no gene for biosynthesis of the glutamic acid oligomer was found in the neighbouring region of that for ePL biosynthesis, and the glutamic acid oligomer was produced by a mutant in which the ePL biosynthetic gene was inactivated by gene disruption.
KawaiT.,
KubotaT.,
HirakiJ.,
IzumiY.2003; Biosynthesis of epsilon-poly l-lysine in a cell-free system of Streptomyces albulus
. Biochem Biophys Res Commun 311:635–640
KellyR. W.,
TaylorP. L.1976; tert-Butyl dimethylsilyl ethers as derivatives for qualitative analysis of steroids and prostaglandins by gas phase methods. Anal Chem 48:465–467
NimuraN.,
KinoshitaT.1986; o-Phthalaldehyde- N-acetyl cysteine as a chiral derivatization reagent for liquid chromatographic optical resolution of amino acid enantiomers and its application to conventional amino acid analysis. J Chromatogr A 352:160–177
NishikawaM.,
OgawaK.2002; Distribution of microbes producing antimicrobial epsilon-poly l-lysine polymers in soil microflora determined by using a novel method. Appl Environ Microbiol 68:3575–3581