title: Chemical structure and biodegradability of halogenated aromatic compounds. Two catechol 1,2-dioxygenases from a 3-chlorobenzoate-grown pseudomonad.
abstract: 1. Two catechol 1,2-dioxygenases, pyrocatechase I and pyrocatechase II, were found in 3-chlorobenzoate-grown cells of Pseudomonas sp. B 13. The latter enzyme showed high relative activities with 3- and 4-chlorocatechol compared with catechol. 2. In benzoate-grown cells, only pyrocatechase I was induced. It was purified 29-fold with a final specific activity of 20 mumol of catechol oxygenated/min per mg of protein and an overall yield of 22%. Because of the instability of pyrocatechase II on chromatography and dialysis, no increase of specific activity was obtained during the purification experiments. 3. Molecular weights of pyrocatechase I and pyrocatechase II were 82000 and 67000 respectively. 4. For both pyrocatechases the pH optimum was found to be at 8.0.5. Inhibitions of the two pyrocatechases by Cu2+ and Hg2+ ions and p-chloromercuribenzoate were different. The effect on pyrocatechase I after incubation for 20 h with the heavy metals was decreased by addition of 1 mM-2-mercaptoethanol to the reaction mixture. The inhibition of pyrocatechase II was even enhanced under these conditions. 6. Extradiol cleavage of 3-methylcatechol in addition to intradiol fission at a ratio of 1:14 was observed only with pyrocatechase I.
mesh_terms: D001565:Benzoates / Q000378:metabolism; D001673:Biodegradation, Environmental; D002396:Catechols; D002413:Cations, Divalent / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D002723:Chlorobenzoates / Q000378:metabolism; D007535:Isomerases / Q000378:metabolism; D008970:Molecular Weight; D010105:Oxygenases / Q000302:isolation & purification / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology*
chemical_list: D001565:Benzoates; D002396:Catechols; D002413:Cations, Divalent; D002723:Chlorobenzoates; D010105:Oxygenases; D007535:Isomerases