title: Salmonella typhimurium mutants defective in acetohydroxy acid synthases I and II.
abstract: An analysis of transposon-induced mutants shows that Salmonella typhimurium possesses two major isozymes of acetohydroxy acid synthase, the enzymes which mediate the first common step in isoleucine and valine biosynthesis. A third (minor) acetohydroxy acid synthase is present, but its significance in isoleucine and valine synthesis may be negligible. Mutants defective in acetohydroxy acid synthase II (ilvG::Tn10) require isoleucine, alpha-ketobutyrate, or threonine for growth, a mutant defective in acetohydroxy acid synthase I (ilvB::Tn5) is a prototroph, and a double mutant (ilvG::Tn10 ilvB::Tn5) requires isoleucine plus valine for growth.
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D005796:Genes; D007532:Isoleucine / Q000096:biosynthesis; D009154:Mutation; D007652:Oxo-Acid-Lyases / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics; D014161:Transduction, Genetic; D014633:Valine / Q000096:biosynthesis / Q000494:pharmacology
chemical_list: D004251:DNA Transposable Elements; D007532:Isoleucine; D000095:Acetolactate Synthase; D007652:Oxo-Acid-Lyases; D014633:Valine