title: Valine accumulation by alpha-aminobutyric acid-resistant mutants of Serratia marcescens.
abstract: alpha-Aminobutyric acid, norvaline, and norleucine, which are analogues of branched-chain amino acids, inhibited the growth of Serratia marcescens. The inhibitory effect of these three analogues was counteracted by branched-chain amino acids. A number of mutants resistant to these analogues were isolated. alpha-Aminobutyric acid-resistant (abu-r) mutants markedly accumulated l-valine in the culture medium, but the other analogue-resistant mutants did not. Acetohydroxy acid synthetase, which seems to be rate-limiting for the biosynthesis of l-valine, was derepressed in abu-r mutants. One of the abu-r mutants, no. 140, which accumulated over 8 mg of l-valine per ml, had about a 20-fold increase in the enzyme level. Most of the abu-r mutants had acetohydroxy acid synthetase activity which was sensitive to feedback inhibition by l-valine to the same extent as in the parent strain. However, the enzyme of two of abu-r mutants was less sensitive to l-valine, and one of the two was the best valine accumulator.
mesh_terms: D000613:Aminobutyrates / Q000494:pharmacology*; D001681:Biological Assay; D002474:Cell-Free System; D003470:Culture Media; D004352:Drug Resistance, Microbial; D004789:Enzyme Activation; D004794:Enzyme Repression; D005827:Genetics, Microbial; D006146:Guanidines; D006836:Hydro-Lyases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007930:Leucine / Q000494:pharmacology; D007934:Leuconostoc / Q000378:metabolism; D008190:Lyases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009153:Mutagens; D009154:Mutation; D009603:Nitroso Compounds; D011773:Pyruvates / Q000378:metabolism; D012706:Serratia marcescens / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013237:Stereoisomerism; D013912:Threonine / Q000378:metabolism; D014633:Valine / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000613:Aminobutyrates; D003470:Culture Media; D006146:Guanidines; D009153:Mutagens; D009603:Nitroso Compounds; D011773:Pyruvates; D013912:Threonine; D008190:Lyases; D006836:Hydro-Lyases; D007930:Leucine; D014633:Valine