Any of a group of substances with antibiotic and antineoplastic properties originally isolated from soil-dwelling microorganisms (actinomycetes) of the genus Streptomyces (formerly Actinomyces).
Actinomycins were the first antibiotics to be isolated from soil bacteria. Their structure contains two peptide loops attached to a planar ring system, which binds to DNA and inhibits its transcription. The most important is actinomycin D, which is used in chemotherapy and biological research.
1940s. From scientific Latin Actinomyces Actinomyces + -in.