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

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Abstract
A new macromolecular peptide antibiotic, AN-3, was isolated from the culture broth of Streptomyces albulus. From 19 l of culture broth containing AN-3 with 90 U/ml activity, a 400 mg sample with a specific activity of 109 U/mg was obtained. Purified AN-3 gave a single band on polyacrylamide gel electrophoresis. AN-3 was a basic polypeptide with a MW of 12,000-12,500 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 H2O, but insoluble in ethanol, butanol and acetone, and was stable at pH 4-9, but unstable at pH 2. AN-3 had no antibacterial activity against the gram-positive and gram-negative bacteria tested. 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 [mouse leukemia cells]; its ED50 was 5 .mu.g/ml. AN-3 had antitumor activity against Lewis [mouse] lung carcinoma in mice.