Screening and some properties of new macromolecular peptide antibiotics

In searching for macromolecular antitumor antibiotics of microbial origin, 2,875 kinds of Actinomycetes culture fluids were applied to a newly developed test system which consisted of antimicrobial assay using a macromolecule permeable mutant, DNA damage assay and mutagenicity test. As a result, 78 macromolecular antibiotics were found. Among them, 15 antibiotics precipitable with ammonium sulfate were macromolecular peptide antibiotics (protein antibiotics), of which molecular weight ranged from 10,000 to 14,000. Macromolecular peptide antibiotics AN-1, -5 and -15, termed type I antibiotics, showed stronger growth inhibitory effect on the uvrA and recA mutants, as compared to the effect on their parent, MP2. They also had mutagenic activity. AN-7, -9, -16, -18, -20, -22, -23, -25, and -26, termed type II, exhibited an increased inhibitory activity to a recA mutant but did not to an uvrA mutant. They all showed mutagenicity. AN-3, -11 and -13, type III antibiotics, gave similar influence on the DNA repair mutants, and on their parent, MP2. They had no mutagenic activity. Except for AN-11 and -13 of type III antibiotics, all antibiotics were inhibitory to the cell growth of a cancer cell, L1210.