title: Characterisation of the enzyme activities involved in the valine biosynthetic pathway in a valine-producing strain of Corynebacterium glutamicum.
abstract: The enzyme activities of the valine biosynthetic pathway and their regulation have been studied in the valine-producing strain, Corynebacterium glutamicum 13032DeltailvApJC1ilvBNCD. In this micro-organism, this pathway might involve up to five enzyme activities: acetohydroxy acid synthase (AHAS), acetohydroxy acid isomeroreductase (AHAIR), dihydroxyacid dehydratase and transaminases B and C. For each enzyme, kinetic parameters (optimal temperature, optimal pH and affinity for substrates) were determined. The first enzyme of the pathway, AHAS, was shown to exhibit a weak affinity for pyruvate (K(m)=8.3 mM). It appeared that valine and leucine inhibited the three first steps of the pathway (AHAS, AHAIR and DHAD). Moreover, the AHAS activity was inhibited by isoleucine. Considering the kinetic data collected during this work, AHAS would be a key enzyme for further strain improvement intending to increase the valine production by C. glutamicum.
authors.affiliation: Laboratoire Bioprocédés Agro-Alimentaires, ENSAIA, Institut National Polytechnique de Lorraine-2, Avenue de la Forêt de Haye, BP 172, F-54505 Vandoeuvre-lès-Nancy cedex, France.
authors.forename: D
authors.initials: D
authors.lastname: Leyval
authors.forename: D
authors.initials: D
authors.lastname: Uy
authors.forename: Stéphane
authors.initials: S
authors.lastname: Delaunay
authors.forename: J L
authors.initials: JL
authors.lastname: Goergen
authors.forename: J M
authors.initials: JM
authors.lastname: Engasser
mesh_terms: D000095:Acetolactate Synthase / Q000737:chemistry / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000597:Amino Acids, Branched-Chain / Q000378:metabolism / Q000494:pharmacology; D003067:Coenzymes / Q000737:chemistry / Q000378:metabolism*; D003352:Corynebacterium / Q000145:classification / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D004795:Enzyme Stability; D006836:Hydro-Lyases / Q000737:chemistry / Q000378:metabolism*; D050540:Ketol-Acid Reductoisomerase; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D013045:Species Specificity; D013379:Substrate Specificity; D000637:Transaminases / Q000737:chemistry / Q000378:metabolism*; D014633:Valine / Q000378:metabolism*
chemical_list: D000597:Amino Acids, Branched-Chain; D003067:Coenzymes; D009097:Multienzyme Complexes; D000429:Alcohol Oxidoreductases; D050540:Ketol-Acid Reductoisomerase; D000095:Acetolactate Synthase; D000637:Transaminases; C019798:branched-chain-amino-acid transaminase; C034522:valine-pyruvate transaminase; D006836:Hydro-Lyases; C020052:dihydroxyacid dehydratase; D014633:Valine