The fermentation, isolation and characterization of a macromolecular peptide antibiotic: AN-3

A new macromolecular peptide antibiotic, named AN-3, was isolated from the culture broth of Streptomyces albulus. From 19 liters of culture broth containing AN-3 with 90 units/ml activity, a 400 mg sample with a specific activity of 109 units/mg was obtained. Purified AN-3 gave a single band on polyacrylamide gel electrophoresis. AN-3 was a basic polypeptide with a molecular weight of 12,000 approximately 12,500 and an isoelectric point of pH 7.6. It showed a peak of absorption at 280 nm and seemed to have no nonprotein chromophoric component. It was soluble in water but insoluble in ethanol, butanol and acetone, and was stable at pH 4 approximately 9 but unstable at pH2. AN-3 had no antibacterial activity against Gram-positive and Gram-negative bacteria so far as tested. But, it showed a strong inhibitory effect on a macromolecule permeable mutant of Escherichia coli. It was not mutagenic. It appeared to inhibit synthesis of DNA and RNA without affecting DNA itself. It also inhibited the in vitro cell growth of L1210 and its ED50 was 5 micrograms/ml. AN-3 had antitumor activity against Lewis lung carcinoma in mouse in vivo.