title: Biosynthesis of monensins A and B: the role of isoleucine.
abstract: Isoleucine added to the cultivation medium of Streptomyces cinnamonensis C-100-5 induced a relative increase of the production of monensin B at the expense of monensin A. U-14C-Isoleucine was found not to be a specific monensin B precursor. The incorporation of 1-13C-2-methylbutyrate into monensins A and B showed the label to be evenly incorporated in both products at carbon atoms originating from C(1) of propionate. In regulatory mutants insensitive to 2-amino-3-chlorobutyrate isoleucine influenced the production of monensins only slightly but strains resistant to 2-aminobutyrate and norleucine decreased their total production by 2-12% in the presence of isoleucine which was associated with a decrease of monensin A content by 14-52%. The inhibitory effect of isoleucine on the biosynthesis of valine, a specific precursor of the butyrate unit of monensin A, is discussed.
mesh_terms: D000613:Aminobutyrates / Q000494:pharmacology; D002087:Butyrates / Q000378:metabolism; D005663:Furans / Q000096:biosynthesis*; D007532:Isoleucine / Q000378:metabolism / Q000494:pharmacology*; D008985:Monensin / Q000031:analogs & derivatives / Q000096:biosynthesis*; D009154:Mutation; D009646:Norleucine / Q000494:pharmacology; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism*; D014633:Valine / Q000096:biosynthesis
chemical_list: D000613:Aminobutyrates; D002087:Butyrates; D005663:Furans; D007532:Isoleucine; C002832:2-amino-3-chlorobutyric acid; C042849:monensin B; D009646:Norleucine; D008985:Monensin; D014633:Valine; C019475:2-methylbutanoic acid