The biosynthetic origin of the carbamoylpolyoxamic sidechain of the polyoxin nucleoside peptide antibiotics was studied using 15N labeled alpha-amino-S-hydroxyvaleric acid as precursor. Gas chromatography mass spectrometry of polyoxamic acid isolated from culture filtrates of Streptomyces cacaoi var. asoensis showed incorporation of the nitrogen atom of alpha-amino-S-hydroxyvaleric acid into carbamoylpolyoxamic acid with an isotopic dilution factor of 23, thus establishing the intermediacy of alpha-amino-S-hydroxyvaleric acid and determination of the full biosynthetic pathway.
