Inhibition of juvenile hormone III biosynthesis by fluoromevalonolactone and citronellyl phenyl imidazoles in isolated corpora allata from the cockroach Periplaneta americana

1-Citronellyl-5-phenyl imidazole (1,5-CPI), 1-citronellyl-4-phenyl imidazole (1,4-CPI) and 1-citronellyl-2-phenyl imidazole (1,2-CPI) were tested as inhibitors of JH-III biosynthesis in vitro. 1,5-CPI was found to be most active followed by 1,2-CPI. The least active isomer was 1,4-CPI. Inhibition of JH biosynthesis by 1,5-CPI resulted in no significant accumulation of the epoxidation substrate methyl farnesoate, and piperonyl butoxide, a known microsomal epoxidase inhibitor, produced only a slight increase in methyl farnesoate. Topical application of fluoromevalonolactone resulted in reduced biosynthetic capability of subsequently excised corpora allata.     

An efficient route to novel 4,5-di- and 2,4,5-tri substituted imidazoles from imidazo[1,5-a]-1,3,5-triazine (5,8-diaza-7,9-dideazapurine) derivatives

Two new types of imidazole derivatives: N-(2-R1-5-R2-1H-imidazol-4-yl) thioureas 7a-g and N-(2-R1-5-R2-1H-imidazol-4-yl) formamides 8b,c,g were obtained in high yields by the hydrolytic degradation of 6-R1-8-R2-2-thioxo-2,3-dihydroimidazo[1,5-a]-1,3,5-triazin-4(1H)-ones 5a-g and 6-R1-8-R2-imidazo[1,5-a]-1,3,5-triazin-4(3H)-ones 6b,c,d, respectively. The tautomeric preferences of the new imidazoles were determined.     

The prebiotic synthesis and catalytic role of imidazoles and other condensing agents

In the past decade significant advances have been made in the synthesis of oligonucleotides and other polymers by means of imidazoles and other condensing agents. In spite of the current knowledge of the chemistry of imidazoles and their importance as prebiotic catalysts, their formation under primitive earth conditions has not been properly demonstrated. We have now been able to synthesize imidazole as well as its 2-methyl and 4-methyl derivatives under plausible prebiotic conditions. One method utilizes an aldehyde (formaldehyde or acetaldehyde), glyoxal and ammonia as the starting materials for the formation of imidazole and 2-methylimidazole. The other method uses a carbohydrate and ammonia as the key reagents for the synthesis of 4-methylimidazole. The importance of imidazole and related compounds (e.g., cyanamide) in the synthesis of oligonucleotides has been studied by us as well as others. Apparently the charge relay group (-N-C-N-) present in imidazoles, carbodiimides, cyanamide, or the histidine and arginine of enzyme active centers is essential for the synthesis of phosphodiester and pyrophosphate bonds.     

The prebiotic synthesis and catalytic role of imidazoles and other condensing agents

In the past decade significant advances have been made in the synthesis of oligonucleotides and other polymers by means of imidazoles and other condensing agents. In spite of the current knowledge of the chemistry of imidazoles and their importance as prebiotic catalysts, their formation under primitive earth conditions has not been properly demonstrated. We have now been able to synthesize imidazole as well as its 2-methyl and 4-methyl derivatives under plausible prebiotic conditions. One method utilizes an aldehyde (formaldehyde or acetaldehyde), glyoxal and ammonia as the starting materials for the formation of imidazole and 2-methylimidazole. The other method uses a carbohydrate and ammonia as the key reagents for the synthesis of 4-methylimidazole. The importance of imidazole and related compounds (e.g., cyanamide) in the synthesis of oligonucleotides has been studied by us as well as others. Apparently the charge relay group (–N–C–N–) present in imidazoles, carbodiimides, cyanamide, or the histidine and arginine of enzyme active centers is essential for the synthesis of phosphodiester and pyrophosphate bonds.     

Imidazole,imidazolate, and hydroxide complexes of (protoporphyrin IX)iron(III) and its dimethyl ester as model systems for ferric hemoproteins: Electron paramagnetic resonance and electronic spectral study

The EPR and electronic spectral changes upon titration of systems consisting of (protoporphyrin IX)iron(III) chloride (Fe(PPIX)Cl) or its dimethyl ester (Fe-(PPIXDME)Cl) and imidazole derivatives with tetrabutylammonium hydroxide solution have been measured at 77 and 298 °K in various solvents. The EPR and electronic spectra of the melt of Fe(PPIXDME)Cl in imidazole derivatives have been also measured. The imidazole derivatives studied here were imidazole and 4-methyl-, 4-phenyl-, 2-methyl-, 2,4-dimethyl-, 1-methyl-, and 1-acetylimidazole. The spectral changes upon addition of hydroxide were markedly different between the systems containing NH imidazoles (BH), with a dissociable proton, and those containing NR imidazoles (BR), without it. In the former systems, five spectral species were successively formed at 77 °K and were assigned to following complexes: [Fe(P)(BH)₂]⁺, Fe(P)(BH)(B), [Fe(P)(B)₂]^?, Fe(P)(BH)(OH), and [Fe(P)(B)(OH)]^?, where P is PPIX or PPIXDME. In the latter systems, initial complex, [Fe(P)(BR)₂]⁺, was found to be changed to final complex, Fe(P)(BR)(OH), through an intermediate at 77 °K. At 298 °K, both systems were found to react with hydroxide to finally form Fe(P)(OH). The crystal field parameters were evaluated using the EPR g values in low-spin complexes studied here and in hemoproteins. The five regions corresponding to five low-spin complexes could be distinguished in crystal field diagrams.     

Structure-activity studies of non-steroidal aromatase inhibitors: the crystal and molecular structures of CGS 16949A and CGS 18320B.

The crystal and molecular structures of 4-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl)benzonitrile hydrochloride (CGS 16949A) and bis(p-cyanophenyl)imidazo-1-yl methane hemisuccinate (CGS 18320B) have been determined as part of structure-activity relationship studies of non-steroidal aromatase inhibitors. CGS 18320B crystallizes with two inhibitor molecules in the asymmetric unit that are similar in conformation. The cyanophenyl groups and the imidazole moieties in the CGS 18320B molecules display a propellor-like arrangement. The orientation of the imidazole ring in CGS 16949A, which is constrained by the piperidine ring, differs by about 80 degrees from the orientations in both CGS 18320B molecules. The conformations of both compounds are consistent with the proposed model (Banting et al. (1988) J. Enz. Inhibit., 2, 216) for inhibitor binding by positioning of the cyanophenyl group in the steroid A-ring binding site and interaction of the imidazole nitrogen with the iron of the haem.     

Herbicide-degrading alpha-keto acid-dependent enzyme TfdA: metal coordination environment and mechanistic insights

TfdA is a non-heme iron enzyme which catalyzes the first step in the oxidative degradation of the widely used herbicide (2, 4-dichlorophenoxy)acetate (2,4-D). Like other alpha-keto acid-dependent enzymes, TfdA utilizes a mononuclear Fe(II) center to activate O(2) and oxidize substrate concomitant with the oxidative decarboxylation of alpha-ketoglutarate (alpha-KG). Spectroscopic analyses of various Cu(II)-substituted and Fe(II)-reconstituted TfdA complexes via electron paramagnetic resonance (EPR), electron spin-echo envelope modulation (ESEEM), and UV-vis spectroscopies have greatly expanded our knowledge of the enzyme's active site. The metal center is coordinated to two histidine residues as indicated by the presence of a five-line pattern in the Cu(II) EPR signal, for which superhyperfine splitting is attributed to two equivalent nitrogen donor atoms from two imidazoles. Furthermore, a comparison of the ESEEM spectra obtained in H(2)O and D(2)O demonstrates that the metal maintains several solvent-accessible sites, a conclusion corroborated by the increase in multiplicity in the EPR superhyperfine splitting observed in the presence of imidazole. Addition of alpha-KG to the Cu-containing enzyme leads to displacement of an equatorial water on copper, as determined by ESEEM analysis. Subsequent addition of 2,4-D leads to the loss of a second water molecule, with retention of a third, axially bound water. In contrast to these results, in Fe(II)-reconstituted TfdA, the cosubstrate alpha-KG chelates to the metal via a C-1 carboxylate oxygen and the alpha-keto oxygen as revealed by characteristic absorption features in the optical spectrum of Fe-TfdA. This binding mode is maintained in the presence of substrate, although the addition of 2,4-D does alter the metal coordination environment, perhaps by creating an O(2)-binding site via solvent displacement. Indeed, loss of solvent to generate an open binding site upon the addition of substrate has also been suggested for the alpha-keto acid-dependent enzyme clavaminate synthase 2 [Zhou et al. (1998) J. Am. Chem. Soc. 120, 13539-13540]. Nitrosyl adducts of various Fe-TfdA complexes have also been investigated by optical and EPR spectroscopy. Of special interest is the tightly bound NO complex of Fe-TfdA.(alpha-KG).(2,4-D), which may represent an accurate model of the initial oxygen-bound species.     

Formation of mu-oxo dimer by the reaction of (meso-tetraphenylporphyrinato)iron(III) with various imidazoles

Reactions between (meso-tetraphenylporphyrinato)iron(III) perchlorate [Fe(tpp)]ClO4 and various imidazoles have been examined in CD2Cl2 solutions. 1H NMR analysis revealed the formation of three kinds of complex; mu-oxo dimer, mono-imidazole adduct, and bis-imidazole adduct. The product ratios changed to a great extent depending on the amount and nature of imidazoles. In general, addition of less than 1.0 equiv of imidazole relative to [Fe(tpp)]ClO4 led to the formation of both mu-oxo dimer and mono-imidazole adduct. However, by the addition of excess amount of imidazole, either the mu-oxo dimer or bis-imidazole adduct was formed exclusively depending on the bulkiness of the imidazole used. In the case of bulky imidazole such as 2-methylbenzimidazole or 2-isopropyl-1-methylimidazole, the mu-oxo dimer was formed quantitatively. In the case of less bulky imidazole such as parent imidazole or 1-methylimidazole, bis-imidazole adduct became the sole product. The results have been explained in terms of the difference in steric interactions between the axial ligands and porphyrin core; the severe steric repulsion prohibits the formation of bis-adduct in the case of bulky imidazoles. As a result, bulky imidazoles prefer to behave as a base; they abstract a proton from coordinated water, and lead to the formation of mu-oxo dimer. Thus, the role of bulky imidazoles in these reactions has some relevance to that of distal histidine in hemoglobin and peroxidase.     

Pyrogalloloestrogens: enzymic methylation of pyrogalloloestrogens and interaction of pyrogalloloestrogens with the enzymic methylation of catecholamines in rat liver in vitro.

During incubation of 2,4-dihydroxyoestrone with the 105000 X g supernatant of rat liver in the presence of S-adenosyl-[Me-14C]methionine, the formation of radioactive mono- as well as dimethyl ether derivatives was demonstrated. The products were identified as: 2,4-dihydroxyoestrone 2-methyl ether, 2,4-dihydroxyoestrone 3-methyl ether, 2,4-dihydroxyoestrone 4-methyl ether, 2,4-dihydroxyoestrone 2,3-dimethyl ether, 2,4-dihydroxyoestrone 2,4-dimethyl ether and 2,4-dihydroxyoestrone 3,4-dimethyl ether. The monomethyl ethers were the main products; within this group the 3-methyl ether of 2,4-dihydroxyoestrone was the main metabolite. Among the dimethyl ether derivatives, the 2,4-dihydroxyoestrone 2,3-dimethyl ether represented the quantitatively most important product. When 2,4-dihydroxyoestrone 2-methyl ether was incubated under the same conditions, 2,4-dihydroxyoestrone 2,3- as well as 2,4-dimethyl ether was formed. The 2,3-dimethyl ether was again the main metabolite. The incubation of 2,4-dihydroxyoestrone 4-methyl ether yielded the 2,4- and 3,4-dimethyl ethers, the first being the main product. In contrast, the 3-methyl ether of 2,4-dihydroxyoestrone was not further methylated by the catechol methyltransferase preparation. In further experiments, the effect of the pyrogalloloestrogen and its monomethyl ether derivatives on the enzymatic methylation of catecholamines was investigated. It was demonstrated that the methylation of adrenalin and dopamine was competitively inhibited by 2,4-dihydroxyoestrone and the 2,4-dihydroxyoestrone monomethyl ethers. Only a weak inhibitory effect was observed with the 3- and 4-monomenthyl ethers (Ki values 200 and 160muM). The unsubstituted pyrogalloloestrogen produced a marked inhibition (Ki value 50muM), but the strongest inhibition was found with the 2-monomethyl ether of 2,4-dihydroxyoestrone (Ki value 14muM). The extent of inhibition caused by the addition of the 2-monomethyl ether of 2,4-dihydroxyoestrone was thereby in the same range as the inhibition caused by pyrogallol and the catecholoestrogens.     

Chemical composition of the essential oils of two Chinese endemic Meconopsis species

The essential oils from two Chinese endemic Meconopsis species, i. e., M. punicea and M. delavayi, were analyzed by using GC-MS for the first time. The major constituents were hexadecanoic acid (16.8%), 1,2-dimethyl naphthalene (11.4%), 1,4-dimethyl naphthalene (6.6%), 1,3-dimethyl-5-ethyl naphthalene (5.9%), and 3-methyl biphenyl (5.6%) for M. punicea, and hexadecanoic acid (9.9%), 1,2-dimethyl naphthalene (7.9%), 1,3-dimethyl-5-ethyl naphthalene (6.2%), tetradecane (5.9%), and hexyl cinnamaldehyde (5.5%) for M. delavayi.     

The effectiveness of inhibitors of soluble prolyl hydroxylase against the enzyme in the cisternae of isolated bone microsomes

Inhibitors of purified, soluble prolyl hydroxylase (K. Majamaa et al. (1984) Eur. J. Biochem. 138, 239-245; K. Majamaa et al. (1986) J. Biol. Chem. 261, 7819-7823) were tested against isolated chick embryo bone microsomes containing intracisternal prolyl hydroxylase and its radiolabeled, unhydroxylated procollagen substrate. Two groups of inhibitors were used which consisted of pyridine-2-carboxylate and 1,2-dihydroxybenzene (catechol) derivatives. The 2,4- and 2,5-pyridine dicarboxylic acids, which are potent inhibitors of the soluble enzyme (Ki values 2 and 0.8 microM, respectively), were effective in the same concentration range against intracisternal prolyl hydroxylase, although their relative affinities were reversed. Inhibition by pyridine-2,4-dicarboxylate in the microsomal system was reversed by increasing the concentration of 2-oxoglutarate. Pyridine-2,4-dicarboxylic acid did not inhibit the uptake of 2-[14C]oxoglutarate into microsomes, so it appears likely that the inhibitor must traverse the microsomal membrane and act directly at the enzyme level. Pyridine-2-carboxylic acid was ineffective in the microsomal system at 1 mM whereas it is a relatively potent inhibitor of the soluble enzyme with a Ki of 25 microM. This finding suggests that the second carboxyl group of the pyridine carboxylate derivatives may be required for their transport into the microsomal lumen. In the soluble system, 3,4-dihydroxybenzoic acid and 1,2-dihydroxybenzene had been found to be competitive inhibitors with relatively low Ki values of 5 and 25 microM, respectively. In the microsomal system, half-maximal inhibition was obtained at approximately 50-100 microM and inhibition was not reversed by increasing the concentrations of either 2-oxoglutarate or ascorbate, alone or together. These results imply that in situ these compounds do not inhibit prolyl hydroxylase directly. Thus, the microsomal system can assess the accessibility of the intracisternal enzyme to potential inhibitors and offers an insight into the in cellulo potential of such compounds.     

Metabolism of naphthalene by the biphenyl-degrading bacterium Pseudomonas paucimobilis Q1

Pseudomonas paucimobilis Q1 originally isolated as biphenyl degrading organism (Furukawa et al. 1983), was shown to grow with naphthalene. After growth with biphenyl or naphthalene the strain synthesized the same enzyme for the ring cleavage of 2,3-dihydroxybiphenyl or 1,2-dihydroxynaphthalene. The enzyme, although characterized as 2,3-dihydroxybiphenyl dioxygenase (Taira et al. 1988), exhibited considerably higher relative activity with 1,2-dihydroxynaphthalene. These results demonstrate that this enzyme can function both in the naphthalene and biphenyl degradative pathway.Abbreviations DHBP dihydroxybiphenyl - DHBPDO 2,3-dihydroxybiphenyl dioxygenase - DHDHNDH 1,2-dihydroxy-1,2-dihydronaphthalene dehydrogenase - DHN 1,2-dihydroxynaphthalene - DHNDO 1,2-dihydroxynaphthalene dioxygenase - HBP cis-2-hydroxybenzalpyruvate - HOPDA 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate - PCB polychlorinated biphenyl - 2NS naphthalene-2-sulfonic acid     

Lack of Staphylococcal Enterotoxin Production among Strains of Staphylococcus aureus from Bovine Mastitis in Denmark

Staphylococcal enterotoxins (SE’s) are a group of small exoproteins produced by some strains of Staphylococcus aureus. The SE’s, designated A to E according to their antigenic specificities, are important causes of food poisoning worldwide. Milk and dairy products are frequently associated with S. aureus enter-otoxin food poisoning, and it is supposed that infected milk from mastitic animals constitute the main source of enterotoxigenic S. aureus of animal origin (Bryon 1983, Gilmour & Harvey 1990, Bergdoll 1989). Indeed, S. aureus is the most common cause of bovine mastitis worldwide, and if mastitis strains produce SE this makes up an enormous reservoir of potential enterotoxin producers. The production of SE by S. aureus isolated from bovine mastitis have been investigated in several countries (Matsunaga et al. 1993, Kenny et al. 1993, Olson et al 1970, Orden et al. 1992, Olsvik et al. 1981, Adekeye 1980, Garcia et al. 1980, Abbar 1986, Harvey & Gilmour 1985). Since no studies have been performed on the prevalence of enterotoxigenic strains of S. aureus isolated from bovine mastitis in Denmark, a well characterized collection of S. aureus (Aarestrup et al. 1995) was investigated with respect to this property.     

Head Space Constituents of Different Varieties of Osmanthus fragrans

This work deals with the head space constituents of different varietiesof Osmanthus fragrans. A porous crosslinked polystyrene resin (Amberite XAD-4)trap was used to absorbing the head space of fresh flowers and the constituents weredetermined by using GC, GC/MS/DS. Thus, fifty six components have been identifiedand thirty seven of them were unreported: i.e. ethyl acetate, 3-methyl butanone, 3-hydroxy-2-butanone, 5-hexen-2-one, 3,3-dimethyl hexane, undecan-6-one, myrcene, decane,limonene,αand β-ocimene, 6-methyl-3, 5-heptadien-2-one,1,6-diacetoxy-hexane,5-phen-ylmethoxy-l-pentanol,3-eyelohexene-l-methanol, ,7-dimethyl-3,5-octadiene, menthone,menthol, ethyl benzaldehyde, 2-cyclohexen-l-yl-2-methyl-5-(1-methylethenyl) acetate, 4-methyl-2-heptanol, 1,4-benzene dicarboxaldehyde, hexyl butanoate, ethyl benzoate, cin-namic aldehyde, 1,4-dimethyl-3-eyclohexen-l-ol ethanone, carvone, 2-hydroxymethyl be-nzoic acid, benzoic acid, 3,4-dihydro-l-2(H)-naphthalenone, 8,8-dimethyl-4-methylene, 1-oxaspiro-[2, 5]-oct-5-ene, 2,4-dimethyl phenyl ethenone, 1-ethoxyethyl benzene, 4,6,6-tri-methyl-bicyelo-[3, 1, 1]-hept-3-en-2-one, 1,4-phenylene bis ethanone-l,1, diethyl O-phtha-late and dibutyl-O-phthalate.     

Occurrence of poly-N-acetyllactosamine synthesis in Sf-9 cells upon transfection of individual human beta-1,4-galactosyltransferase I, II, III, IV, V and VI cDNAs

Lectin blot analysis of membrane glycoprotein samples from Sf-9 cells upon transfection of individual human beta-1,4-galactosyltransferase (beta-1,4-GalT) I, II, III, IV, V et VI cDNAs showed that the endogenous N-linked oligosaccharides are galactosylated (Guo et al., Glycobiology (2001), in press). Further analysis revealed that membrane glycoprotein samples from all the gene-transfected cells are also reactive to Lycopersicon esculentum agglutinin (LEA) et Datura stramonium agglutinin (DSA), both of which bind to oligosaccharides with poly-N-acetyllactosamine chains while no lectin reactive protein bands are detected when blots are pretreated with a mixture of diplococcal beta-1,4-galactosidase et jack bean beta-N-acetylhexosaminidase or N-glycanase. Analysis of endo-beta-galactosidase-digestion products revealed the presence of the Gal1-->GlcNAc1-->Gal and/or GlcNAc1-->Gal structures in the gene-transfected cells. When the homogenates of the gene-transfected cells were used as enzyme sources towards oligosaccharides with the GlcNAc beta 1-->(3Gal beta 1-->4GlcNAc)(1-3) structures, human recombinant beta-1,4-GalTs I et II galactosylated these oligosaccharides more effectively than other beta-1,4-GalTs. These results indicate that beta-1,4-GalTs I-VI can synthesize poly-N-acetyllactosamine chains with beta-1,3-N-acetylglucosaminyltransferase.     

Optimization of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of HIV capsid assembly inhibitors 1: Addressing configurational instability through scaffold modification

The optimization of a 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly that possess a labile stereocenter at C3 is described. Quaternization of the C3 position of compound 1 in order to prevent racemization gave compound 2, which was inactive in our capsid disassembly assay. A likely explanation for this finding was revealed by in silico analysis predicting a dramatic increase in energy of the bioactive conformation upon quaternization of the C3 position. Replacement of the C3 of the diazepine ring with a nitrogen atom to give the 1,5-dihydro-benzo[f][1,3,5]triazepine-2,4-dione analog 4 was well tolerated. Introduction of a rigid spirocyclic system at the C3 position gave configurationally stable 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione analog 5, which was able to access the bioactive conformation without a severe energetic penalty and inhibit capsid assembly. Preliminary structure–activity relationships (SAR) and X-ray crystallographic data show that knowledge from the 1,5-dihydrobenzo[b][1,4]diazepine-2,4-dione series of inhibitors of HIV-1 capsid assembly can be transferred to these new scaffolds.     

Synthesis, biological evaluation and molecular modeling of 1,2,3-triazole analogs of combretastatin A-1

The synthesis, cytotoxicity, inhibition of tubulin polymerization data and anti-angiogenetic effects of seven 1,5-disubstituted 1,2,3-triazole analogs and two 1,4-disubstituted 1,2,3-triazole analogs of combretastatin A-1 (1) are reported herein. The biological studies revealed that the 1,5-disubstituted 1,2,3-triazoles 3-methoxy-6-(1-(3,4,5-trimethoxyphenyl)-1H-1,2,3-triazol-5-yl)benzene-1,2-diol (6), 3-methoxy-6-(1-(3,4,5-trimethoxyphenyl)-1H-1,2,3-triazol-5-yl)benzene-1,2-diamine (8) and 5-(2,3-difluoro-4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-1H-1,2,3-triazole (9) were the three most active compounds regarding inhibition of both tubulin polymerization and angiogenesis. Molecular modeling studies revealed that combretastatins 1 and 2 and analogs 5-11 could be successfully docked into the colchicine binding site of α,β-tubulin.     

Degradation of 2,4-dinitrotoluene by the lignin-degrading fungus Phanerochaete chrysosporium.

Under ligninolytic conditions, the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dinitrotoluene (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell extracts. The multistep pathway involves the initial reduction of I to yield 2-amino-4-nitrotoluene (II). II is oxidized by MnP to yield 4-nitro-1,2-benzoquinone (XII) and methanol. XII is then reduced to 4-nitro-1,2-hydroquinone (V), and the latter is methylated to 1,2-dimethoxy-4-nitrobenzene (X). 4-Nitro-1,2-hydroquinone (V) is also oxidized by MnP to yield nitrite and 2-hydroxybenzoquinone, which is reduced to form 1,2,4-trihydroxybenzene (VII). 1,2-Dimethoxy-4-nitrobenzene (X) is oxidized by LiP to yield nitrite, methanol, and 2-methoxy-1,4-benzoquinone (VI), which is reduced to form 2-methoxy-1,4-hydroquinone (IX). The latter is oxidized by LiP and MnP to 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (VII). The key intermediate 1,2,4-trihydroxybenzene is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid. In this pathway, initial reduction of a nitroaromatic group generates the peroxidase substrate II. Oxidation of II releases methanol and generates 4-nitro-1,2-benzoquinone (XII), which is recycled by reduction and methylation reactions to regenerate intermediates which are in turn substrates for peroxidase-catalyzed oxidation leading to removal of the second nitro group. Thus, this unique pathway apparently results in the removal of both aromatic nitro groups before ring cleavage takes place.     

Degradation of 2,4-dinitrotoluene by the lignin-degrading fungus Phanerochaete chrysosporium.

Under ligninolytic conditions, the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dinitrotoluene (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell extracts. The multistep pathway involves the initial reduction of I to yield 2-amino-4-nitrotoluene (II). II is oxidized by MnP to yield 4-nitro-1,2-benzoquinone (XII) and methanol. XII is then reduced to 4-nitro-1,2-hydroquinone (V), and the latter is methylated to 1,2-dimethoxy-4-nitrobenzene (X). 4-Nitro-1,2-hydroquinone (V) is also oxidized by MnP to yield nitrite and 2-hydroxybenzoquinone, which is reduced to form 1,2,4-trihydroxybenzene (VII). 1,2-Dimethoxy-4-nitrobenzene (X) is oxidized by LiP to yield nitrite, methanol, and 2-methoxy-1,4-benzoquinone (VI), which is reduced to form 2-methoxy-1,4-hydroquinone (IX). The latter is oxidized by LiP and MnP to 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (VII). The key intermediate 1,2,4-trihydroxybenzene is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid. In this pathway, initial reduction of a nitroaromatic group generates the peroxidase substrate II. Oxidation of II releases methanol and generates 4-nitro-1,2-benzoquinone (XII), which is recycled by reduction and methylation reactions to regenerate intermediates which are in turn substrates for peroxidase-catalyzed oxidation leading to removal of the second nitro group. Thus, this unique pathway apparently results in the removal of both aromatic nitro groups before ring cleavage takes place.