Metabolism of 4-chloro-2-methylphenoxyacetate by a soil pseudomonad. Ring-fission, lactonizing and delactonizing enzymes.
1. A cell-free system, prepared from Pseudomonas N.C.I.B. 9340 grown on 4-chloro-2-methylphenoxyacetate (MCPA) was shown to catalyse the reaction sequence: 5-chloro-3-methylcatechol --> cis-cis-gamma-chloro-alpha-methylmuconate --> gamma-carboxymethylene-alpha-methyl-Delta(alphabeta)-butenolide --> gamma-hydroxy-alpha-methylmuconate. 2. The activity of the three enzymes involved in these reactions was completely resolved and the lactonizing and delactonizing enzymes were separated. 3. This part of the metabolic pathway of 4-chloro-2-methylphenoxyacetate is thus confirmed for this bacterium. 4. The ring-fission oxygenase required Fe(2+) or Fe(3+) and reduced glutathione for activity; the lactonizing enzyme is stimulated by Mn(2+), Mg(2+), Co(2+) and Fe(2+); no cofactor requirement could be demonstrated for the delactonizing enzyme. 5. cis-cis-gamma-Chloro-alpha-methylmuconic acid was isolated and found to be somewhat unstable, readily lactonizing to gamma-carboxymethylene-alpha-methyl-Delta(alphabeta)-butenolide. 6. Enzymically the lactonization appears to be a single-step dehydrochlorinase reaction.
D002396:Catechols / Q000378:metabolism; D003035:Cobalt; D003470:Culture Media; D005978:Glutathione / Q000378:metabolism; D006016:Glycolates / Q000378:metabolism*; D006540:Herbicides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D007783:Lactones / Q000378:metabolism; D008274:Magnesium; D008345:Manganese; D010105:Oxygenases; D011549:Pseudomonas / Q000378:metabolism*; D012988:Soil Microbiology
D002396:Catechols; D003470:Culture Media; D006016:Glycolates; D006540:Herbicides; D007783:Lactones; D003035:Cobalt; D008345:Manganese; D007501:Iron; D010105:Oxygenases; D005978:Glutathione; D008274:Magnesium