Biodegradation of 4-methyl-5-nitrocatechol by Pseudomonas sp. strain DNT.
Pseudomonas sp. strain DNT degrades 2,4-dinitrotoluene (DNT) by a dioxygenase attack at the 4,5 position with concomitant removal of the nitro group to yield 4-methyl-5-nitrocatechol (MNC). Here we describe the mechanism of removal of the nitro group from MNC and subsequent reactions leading to ring fission. Washed suspensions of DNT-grown cells oxidized MNC and 2,4,5-trihydroxytoluene (THT). Extracts prepared from DNT-induced cells catalyzed the disappearance of MNC in the presence of oxygen and NADPH. Partially purified MNC oxygenase oxidized MNC in a reaction requiring 1 mol of NADPH and 1 mol of oxygen per mol of substrate. The enzyme converted MNC to 2-hydroxy-5-methylquinone (HMQ), which was identified by gas chromatography-mass spectrometry. HMQ was also detected transiently in culture fluids of cells grown on DNT. A quinone reductase was partially purified and shown to convert HMQ to THT in a reaction requiring NADH. A partially purified THT oxygenase catalyzed ring fission of THT and accumulation of a compound tentatively identified as 3-hydroxy-5-(1-formylethylidene)-2-furanone. Preliminary results indicate that this compound is an artifact of the isolation procedure and suggest that 2,4-dihydroxy-5-methyl-6-oxo-2,4-hexadienoic acid is the actual ring fission product.
Haigler
B E
BE
Armstrong Laboratory, EQC-OL, Tyndall Air Force Base, Florida 32403-5323.
Nishino
S F
SF
Spain
J C
JC
D001673:Biodegradation, Environmental; D002396:Catechols / Q000378:metabolism*; D004136:Dinitrobenzenes / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D013058:Mass Spectrometry; D008954:Models, Biological; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000302:isolation & purification; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism; D014050:Toluene / Q000031:analogs & derivatives / Q000378:metabolism
C087487:2,4-dihydroxy-5-methyl-6-oxo-2,4-hexadienoic acid; C087486:4-methyl-5-nitrocatechol; D002396:Catechols; D004136:Dinitrobenzenes; D005231:Fatty Acids, Unsaturated; D011809:Quinones; C087485:2,4,5-trihydroxytoluene; D014050:Toluene; D009249:NADP; C087484:2-hydroxy-5-methylquinone; C016403:2,4-dinitrotoluene; D016660:NAD(P)H Dehydrogenase (Quinone); D010100:Oxygen