N-methylphenylalanyl-dehydrobutyrine diketopiperazine, an A-factor mimic that restores antibiotic biosynthesis and morphogenesis in Streptomyces globisporus 1912-B2 and Streptomyces griseus 1439

The cell-free extracts of a landomycin E-producing strain, Streptomyces globisporus 1912-2, were shown to contain a low-molecular-weight compound that, like A-factor, restored the landomycin E and streptomycin biosynthesis and sporulation of the defective mutants S. globisporus 1912-B2 and S. griseus 1439, respectively. The compound was purified by thin layer chromatography and HPLC. It had an absorption maximum at λ max =245 nm and a molecular mass of m/z 244. On the basis of NMR spectroscopy (1 H, 13 C, HSQC, HMBC, COSY and NOE) the chemical structure of the compound was elucidated as 6-benzyl-3-eth-(Z)-ylidene-1-methyl-piperazine-2,6-dione ((L)-N-methylphenylalanyl-dehydrobutyrine diketopiperazine (MDD)). The sequences of arpA genes in S. globisporus 1912-2 and S. griseus NBRC 13350 are highly conserved. An explanation for the observed biological activity of MDD was proposed.