Effective production of dehydro cyclic dipeptide albonoursin exhibiting pronuclear fusion inhibitory activity II. Biosynthetic and bioconversion studies

Albonoursin production was greatly enhanced when cycle (L-Leu-L-Phe) (CFL), a tetrahydro derivative of albonoursin, was added to the 2-day culture of an albonoursin-producing actinomycete, Streptomyces albulus KO-23. The incr ease in albonoursin production paralleled the amount of CFL added. Furtherm ore, the resting cells of the strain catalyzed the bioconversion of CFL to albonoursin. The optimum pH and temperature for the conversion were found t o be pH 10.0 and 50 degrees C. The feeding experiments and the resting-cell reactions revealed that albonoursin is biosynthesized by dehydrogenation o f CFL in the actinomycete. This is the first report for a dehydrogenation o f amino acid residues at the alpha,beta-positions in cyclic dipeptides.