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PubMed1990

Induction of acropetal (14)C-photosynthate transport and radial growth by indole-3-acetic acid in Pinus sylvestris shoots.

The relationship between radial growth and assimilate movement was determined in one-year-old Pinus sylvestris (L.) cuttings collected during the dormant period and reactivated for 1-27 days under environmental conditions favorable for growth. The cuttings were either left with buds intact, defoliated along the distal 8 cm, or debudded and treated apically with 0 or 1 mg g(-1) indole-3-acetic acid (IAA) in lanolin. Radial growth was measured as tracheid production and bark radial width. The distribution of (14)C-photosynthate 1 or 5 days after exposure to (14)CO(2) was used to indicate assimilate movement. Debudding inhibited tracheid production and decreased acropetal (14)C-photosynthate transport, whereas applying IAA to debudded cuttings promoted both these processes and, in addition, induced vigorous callus growth within the bark immediately below the application point. Distal defoliation markedly increased the amount of (14)C-photosynthate transported toward the apex without altering how debudding and exogenous IAA affected tracheid production and the distribution of (14)C-photosynthate. The production of tracheids induced by apically applied IAA in debudded and distally defoliated cuttings increased progressively in material collected on September 9, October 14 and November 24, whereas bark radial width and acropetal (14)C-photosynthate movement increased only between the first two collection dates. Ringing midway between the IAA source and the bottom of the distally defoliated region with a lanolin mixture of 10 mg g(-1)N-1-naphthylphthalamic acid (NPA), 1 mg g(-1) methyl-2-chloro-9-hydroxy-fluorene-9-carboxylic acid (CF) or 10 mg g(-1) phenylacetic acid (PAA) reduced radial growth and [1-(14)C]IAA transport below the ring and locally promoted radial growth and accumulated radioactivity above. (14)C-Photosynthate transport into the region above the ring either was not altered (CF, PAA) or was increased (NPA). The results indicate that apically applied IAA induces the acropetal movement of (14)C-photosynthate in debudded P. sylvestris shoots by locally promoting activity correlated with tracheid and callus production rather than by affecting radial growth or phloem transport processes, or both, at a distance below the IAA source.

Journal Article↗

PubMed1998

Peroral administration of specific antibody enhances carcinogen excretion.

Ingested carcinogens may exert effects directly on the gastrointestinal epithelium or after absorption and transport to other tissues. To determine the effect of anti-carcinogen antibody ingestion on dietary carcinogen excretion, a mixture of specific IgA or IgG and the model carcinogen 125I-N-2-(4-hydroxyphenyl-acetamido) fluorene (125I-pHP-AAF) was perorally administered to mice. These mice excreted more total and antibody-bound radiotracer in feces compared with controls given a similar mixture containing nonspecific antibody. In addition, urinary radiotracer excretion was reduced by 96% in specific-antibody dosed mice, indicating reduced gastrointestinal absorption of 125I-pHP-AAF. Reduced radiotracer absorption was also reflected by a 56% reduction in radiotracer content in tissues from mice receiving specific antibody. Other mice received peroral IgA before i.p. injection of 125I-PH-AAF. Specific antibody treatment consistently increased intraluminal radiotracer sequestration, as indicated by the level of total and antibody-bound radiotracer partitioning to aqueous fecal extracts. Similarly, when a mixture of 125I-pHP-AAF and IgG were injected directly into the small intestine, more radioactivity appeared in the feces of mice given specific antibody. High-performance liquid chromatography analysis of aqueous fecal extracts indicated that the majority of fecal radiotracer from specific-antibody dosed mice was unmetabolized parent compound. Thus, peroral administration of AAF-specific antibodies mixed with 125I-pHP-AAF decreased gastrointestinal absorption and increased fecal excretion of the radiotracer, suggesting a novel mechanism for protection against environmental carcinogens.

2-Acetylaminofluorene↗

PubMed2003

Alkanindiges illinoisensis gen. nov., sp. nov., an obligately hydrocarbonoclastic, aerobic squalane-degrading bacterium isolated from oilfield soils.

An alkane-degrading bacterium, designated GTI MVAB Hex1(T), was isolated from chronically crude oil-contaminated soil from an oilfield in southern Illinois. The isolate grew very weakly or not at all in minimal or rich media without hydrocarbons. Straight-chain aliphatic hydrocarbons, such as hexadecane and heptadecane, greatly stimulated growth; shorter-chain (</=C(15)) hydrocarbons did not (with decane as the sole exception). Growth was also greatly enhanced by the branched aliphatic hydrocarbons pristane and squalane. The latter of these was most intriguing, as catabolism of squalane has hitherto been reported only for Mycobacterium species. Although unable to utilize mono- or polycyclic aromatic hydrocarbons as sole carbon sources, the isolate did show slight fluorene-mineralizing capability in Luria-Bertani medium, which was partially repressed by hexadecane. In contrast, hexadecane supplementation greatly increased mineralization of (14)C-dodecane, which was not a growth substrate. Further testing emphasized the isolate's extremely narrow substrate range, as only Tween 40 and Tween 80 supported significant growth. Microscopic examination (by scanning and transmission electron microscopy) revealed a slightly polymorphic coccoidal to bacillar morphology, with hydrocarbon-grown cells tending to be more elongated. When grown with hexadecane, GTI MVAB Hex1(T) accumulated a large number of electron-transparent intracytoplasmic inclusion bodies. These were also prevalent during growth in the presence of squalane. Smaller inclusion bodies were observed occasionally with pristane supplementation; they were, however, absent during growth on crude oil. On the basis of 16S rRNA gene sequence data and range of growth substrates, classification of this isolate as the type strain of Alkanindiges illinoisensis gen. nov., sp. nov. is proposed, which is most closely related (approx. 94 % sequence similarity) to Acinetobacter junii.

Aerobiosis↗

PubMed2003

1,3-thiazolidine derivatives from regioselective [2+3]-cycloadditions of azomethine ylides with thioketones.

The title compounds, namely dimethyl (2RS)-2,3-diphenyl-1,3-thiazolidine-5-spiro-2'-adamantane-4,4-dicarboxylate methanol solvate, C(28)H(31)NO(4)S.0.275CH(4)O, and dimethyl (4RS)-3,4-diphenyl-1,3-thiazolidine-5-spiro-9'-(9'H-fluorene)-2,2-dicarboxylate, C(31)H(25)NO(4)S, were obtained from dipolar [2+3]-cycloadditions of an azomethine ylide with adamantanethione and thiofluorenone, respectively. The structures show that the choice of thioketone affects the regioselectivity of the cycloaddition. The asymmetric unit of the former structure contains two molecules of the thiazolidine derivative plus a site for a partial occupancy (55%) methanol molecule. O-H...O and C-H...O interactions link two of each of these entities into closed centrosymmetric hexamers. The five-membered ring in each structure has an envelope conformation.

Journal Article↗

PubMed2004

A new photochromic tetrahydroindolizine.

The title compound, dimethyl 10b'-(4-fluorostyryl)-8',9'-dimethoxy-4-nitro-5',6'-dihydrospiro[9H-fluorene-9,1'(10b'H)-pyrrolo[2,1-a]isoquinoline]-2',3'-dicarboxylate, C38H31FN2O8, is a new photochromic tetrahydroindolizine. One of the C-C bonds at the spiro C atom is very long [1.630 (2) A], thus explaining the photochromic behaviour.

Journal Article↗

PubMed2003

Structure and degree of charge transfer of two polymorphs of a 1:1 molecular complex: [2,2'-bis-1,3-dithiole][9-dicyanomethylene-4,5,7-trinitrofluorene-2-carboxylic acid methyl ester] (TTF-MeDC2TNF).

A new organic charge-transfer complex, C(18)H(7)N(5)O(8).C(6)H(4)S(4), has been prepared using TTF (tetrathiafulvalene) as a donor (D) and MeDC2TNF (9-dicyanomethylene-4,5,7-trinitro-fluorene-2-carboxylic acid methyl ester) as an acceptor (A). Two monoclinic polymorphs of the 1:1 salt were crystallized and characterized by X-ray diffraction. Form alpha crystallizes in space group P2(1)/n with Z' = 1, while form beta crystallizes in space group C2/c with Z' = 1/2 and the MeDC2TNF moiety disordered across a twofold axis. Both phases have mixed-stack crystal packings, which are characteristic of semiconducting one-dimensional organic complexes. However, the observed crystal packings are significantly different, with a single D...A interlayer separation of 3.452 A for the disordered beta polymorph and interlayer separations of 3.378 and 3.483 A in the case of the ordered alpha form. These variations are reflected in the degree of charge transfer, delta, which was estimated on the basis of the b(2u) stretching-mode frequency shift observed in the IR spectra for the cyano groups of the MeDC2TNF radical anion. The fact that the charge transfer is more efficient for alpha-(TTF-MeDC2TNF) than for beta-(TTF-MeDC2TNF) (delta = 0.35 and 0.31, respectively) is consistent with the structural features observed for each crystalline form.

Journal Article↗

PubMed1996

Degradation of crude oil by Acinetobacter calcoaceticus and Alcaligenes odorans.

Two types of Indian crude oil (Bombay High and Gujarat) were tested for their biodegradability by Acinetobacter calcoaceticus and Alcaligenes odorans. Acinetobacter calcoaceticus S30 and Alc. odorans P20 degraded Bombay High crude oil by 50% and 45%, while only 29% and 37% of Gujarat crude oil (heavy crude oil) was degraded by these isolates, respectively. Acinetobacter calcoaceticus and Alc. odorans in combination degraded 58% and 40% of Bombay High and Gujarat crude oils, respectively, which were significantly higher than that of by individual cultures. Acinetobacter calcoaceticus S30 degraded more of the alkanes fraction than the aromatics fraction of both crude oils. GC fingerprinting of alkane fraction showed major degradation of heptadecane (C17), octadecane (C18), nonadecane (C19), eicosane (C20), docosane (C22), tricosane (C23) and tetracosane (C24) of crude oil, while the Alc. odorans P20 degraded alkanes and aromatics equally. The asphaltenic component increased in both types of crude oil after biodegradation . The two strains grew very well on n-alkane up to C33 as well as on pristane (branched-chain alkane) but could not grow on cycloalkanes. Acinetobacter calcoaceticus S30 could not grow on pure polycyclic aromatic hydrocarbon (PAH) compounds except naphthalene but Alc. odorans P20 could grow on anthracene, phenanthrene, dibenzothiophene, fluorene, fluoranthene, pyrene and chrysene.

Acinetobacter calcoaceticus↗

PubMed1994

Multiple peptide synthesis on acid-labile handle derivatized polyethylene supports.

Using the multipin peptide synthesis approach, a range of peptides with native amide and carboxylate C-termini were generated using an acid-labile approach. Polyethylene crowns grafted with hydroxyethylmethacrylate (HEMA) polymer were functionalized with either 4-hydroxymethylphenoxyacetic acid for the generation of peptide-carboxylate or p-[(R,S)-alpha-[1-(9H-fluoren-9-yl)methoxyformamido]-2,4-dim ethoxy- benzyl]phenoxyacetic acid for peptide-amide. A range of known peptide hormone sequences and other peptides with native C-termini were assembled by sequential incorporation of N alpha-Fmoc protected amino acids. Peptides were sidechain deprotected and cleaved from crowns with TFA/scavengers within 2 mL centrifuge tubes, and isolated by a series of ether/petrol wash and centrifugation steps. In this way it was possible to avoid a cleavage and isolation botteneck, allowing rapid processing of large numbers of peptides.

Amino Acid Sequence↗

PubMed1996

Peptide synthesis on chitin.

The use of chitin as a support for solid-phase peptide synthesis is described and illustrated by synthesis of four peptides, varying in length from 10 to 29 residues. Syntheses were performed in a continuous-flow peptide synthesizer, using Fmoc chemistry. A cleavable linker, p-[(R,S)-alpha-[1-(9H-fluoren-9-yl)-methoxyformamido]-2,4-di methoxybenzyl]- phenoxyacetic acid, was attached to chitosan at the desired substitution level, and the complex acetylated to yield a linker substituted chitin. The effects of temperature, solvents and degree of linker substitution on the syntheses were studied. Acyl carrier peptide (ACP) synthesis studies indicated that temperature was the single most important parameter. Increasing the temperature of the synthesis from 20 to 55 degrees C resulted in an enormous improvement of this synthesis, with about 90% of the crude product being the correct peptide. Denaturing solvents, such as DMSO, could be used without significant effect on the flow properties of the support. The synthesis of one peptide was mainly improved by lowering the degree of substitution from 0.3 to 0.1 mmol/g, suggesting peptide aggregation was a problem in this case. The results of three syntheses on chitin were comparable with those obtained with a commonly used commercial support. This work shows that, under appropriate conditions, chitin can be utilized directly as a support for peptide synthesis.

Amino Acid Sequence↗

PubMed1997

Peptide synthesis on Sepharose beads.

NHS-activated Pharmacia HiTrap Sepharose was modified with 1, 3-diaminopropane to give an amino-functionalized support suitable for solid-phase peptide synthesis. The amide linker p-[(R1S)-alpha-[1-(9H-fluoren-9-yl)-methoxyformamido]- 2, 4-dimethoxybenzyl]phenoxyacetic acid was incorporated and the acyl carrier protein sequence 65-74 was synthesized manually on this support by the Fmoc procedure under controlled conditions with monitoring of the coupling reactions. The performance of the support in automated multiple synthesis in open reactors, with an Abimed AMS 422 according to standard protocols, was evaluated by the synthesis of the acyl carrier protein sequence 65-74 and two other 15-mer and 18-mer peptides. The quality of the resulting crude peptides was determined by HPLC and MALDI-MS, and compared with the same sequences synthesized in parallel on the commercial peptide synthesis resin TentaGel S RAM. The modified HiTrap material was found to be particularly suited for Fmoc solid-phase peptide synthesis and should be advantageous for the utilization of immobilized peptides and peptide libraries in biological assays.

Acyl Carrier Protein↗

PubMed1986

Induction of different isozymes of cytochrome P-450 and of microsomal epoxide hydrolase in rat liver by 2-acetylaminofluorene and structurally related compounds.

The amounts of five different forms of cytochrome P-450 and of microsomal epoxide hydrolase were determined immunochemically in rat liver microsomes before and after treatment of the animals with 2-acetylaminofluorene and 15 structurally related compounds. The amount of cytochrome P-450c was found to be increased about 60-fold after treatment with 2-aminofluorene and 3-aminofluorene. Administration of 1-aminofluorene, 4-aminofluorene, 2-acetylaminofluorene and nitrofluorene increased this isozyme about 15-19 times. 2-Aminofluorene was found to inhibit the binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin to a cytoplasmic receptor 50% at a concentration of 3.12 microM, while no such inhibition could be detected with 2-acetylaminofluorene. Induction of ethoxyresorufin O-deethylase activity was found to be highly correlated (+0.95) with the induction of cytochrome P-450c. Also correlated with the induction of this form was the amount of cytochrome P-450d (+0.84), which could be maximally increased about fourfold. Cytochromes P-450b + e were induced by 2-acetylaminofluorene, 4-acetylaminofluorene and fluorene (about tenfold), while 4-aminofluorene and 4-acetylaminofluorene were found to elevate cytochrome P-450PB/PCN-E about threefold. Microsomal epoxide hydrolase was induced by many of the compounds tested, with 2,7-diaminofluorene, 2,7-diacetylaminofluorene, 2-acetylaminofluorene and 2-(N-hydroxy)acetylaminofluorene being the most potent. No correlation of the induction of this enzyme with the induction of any isozyme of cytochrome P-450 was observed.

2-Acetylaminofluorene↗

PubMed1994

Complete L-alanine scan of neuropeptide Y reveals ligands binding to Y1 and Y2 receptors with distinguished conformations.

The synthesis of more than fifty 36-residue oligopeptide analogs of neuropeptide Y (NPY) and their affinity to human Y1 and Y2 receptors is described. Each amino acid of the natural sequence was replaced by L-alanine, the four alanine residues at position 12, 14, 18 and 23 were replaced by glycine. Additional residues were exchanged to closely related ones in order to characterize the prerequisites for binding. A combination of automated single and multiple peptide synthesis using fluoren-9-ylmethoxycarbonyl/tert-butoxy strategy was applied. The purified peptides were characterized by electrospray mass spectrometry, analytical HPLC and amino acid analysis. Binding was investigated by displacement of 125I-labelled neuropeptide Y from human neuroblastoma cell lines SK-N-MC and SMS-KAN. Whereas Pro2 and the integrity of the neuropeptide Y loop is important for the binding to the Y1 receptor, exchanges within the C-terminal helix affect the affinity to the Y2 receptor. The C-terminal pentapeptide amide is important for both receptors and probably represents the binding site. However, Arg33 and Arg35 may not be exchanged by L-alanine in the Y1 system, whereas Arg35 and Tyr36 are the most susceptible residues in the Y2 system. In order to distinguish between conformational effects and direct hormone/receptor interaction via the side chains of neuropeptide Y, circular dichroic studies of the alanine-containing peptides were performed and structure affinity relationships are discussed. Comparing the affinities of the neuropeptide Y analogs to Y1 and Y2 receptors significant differences were found for the two binding sites, which suggests a different active conformation of neuropeptide Y at the two subtypes of receptors. Using molecular dynamics calculations, two distinct conformations were identified which are in good agreement with the data obtained by structure/affinity investigations.

Amino Acid Sequence↗

PubMed2007

Determining the identity and roles of oil-metabolizing marine bacteria from the Thames estuary, UK.

Crude oil is a complex mixture of different hydrocarbons. While diverse bacterial communities can degrade oil, the specific roles of individual members within such communities remain unclear. To identify the key bacterial taxa involved in aerobic degradation of specific hydrocarbons, microcosm experiments were established using seawater from Stanford le Hope, Thames estuary, UK, adjacent to a major oil refinery. In all microcosms, hydrocarbon degradation was significant within 10 weeks, ranging from > 99% of low-molecular-weight alkanes (C(10)-C(18)), 41-84% of high-molecular-weight alkanes (C(20)-C(32)) and pristane, and 32-88% of polycyclic aromatic hydrocarbons (PAHs). Analysis of 16S rRNA sequences from clone libraries and denaturing gradient gel electrophoresis (DGGE) indicated that, except when incubated with fluorene, PAH-degrading communities were dominated by Cycloclasticus. Moreover, PAH-degrading communities were distinct from those in microcosms containing alkanes. Degradation of the branched alkane, pristane, was carried out almost exclusively by Alcanivorax. Bacteria related to Thalassolituus oleivorans (99-100% identity) were the dominant known alkane degraders in n-alkane (C(12)-C(32)) microcosms, while Roseobacter-related bacteria were also consistently found in these microcosms. However, in contrast to previous studies, Thalassolituus, rather than Alcanivorax, was dominant in crude oil-enriched microcosms. The communities in n-decane microcosms differed from those in microcosms supplemented with less volatile alkanes, with a phylogenetically distinct species of Thalassolituus out-competing T. oleivorans. These data suggest that the diversity and importance of the genus Thalassolituus is greater than previously established. Overall, these experiments demonstrate how degradation of different petroleum hydrocarbons is partitioned between different bacterial taxa, which together as a community can remediate petroleum hydrocarbon-impacted estuarine environments.

Biodegradation, Environmental↗

PubMed1957

Phramacological properties of esters of 1-alkyl-2-hydroxyalkylpyrrolidine and their quaternary derivatives.

A series of esters of 1-alkyl-2-hydroxyalkylpyrrolidine and their quaternary derivatives have been shown to possess significant anti-acetylcholine activity. The benzilic acid esters were the most active, followed by xanthene-9-carboxylic acid, fluorene-9-carboxylic acid and diphenylacetic acid esters in that order. The quaternary derivatives were more active than their corresponding tertiary compounds both in vivo and in vitro. The most active compound of the series tested in vivo was (1-methylpyrrolid-2-yl)methyl benzilate methiodide and was as potent as atropine. There was a progressive decrease in anti-acetylcholine activity and a proportional increase in local anaesthetic activity as the number of carbon atoms was increased from 1 to 3 in the pyrrolidyl side-chain of the tertiary salts of the benzilic acid ester series. Likewise increasing the size of the group on the nitrogen atom led to a decrease in anti-acetylcholine activity and an increase in local anaesthetic activity. Quaternization of the tertiary salts resulted in a loss of local anaesthetic activity. Most of the compounds tested possessed some antihistamine properties, while papaverine-like activity was confined to the tertiary salts only. No significant neuromuscular blocking activity was evident.

Acetylcholine↗

PubMed1978

Evidence for the participation of beta1-adrenoceptors in isoprenaline-induced renin release from rat kidny slices in vitro.

1. The inhibitory effects were studied of 4 beta-adrenoceptor antagonists against renin release induced by isoprenaline (0.5 mumol/1) in rat kidney slices. Additionally the pA2 values of these 4 drugs were measured against isoprenaline in guinea-pig isolated atria and trachea (against beta1- and beta2-adrenoceptors respectively). 2 When employed at a concentration of 2 mumol/1 propranolol and atenolol significantly inhibited renin release (P less than 0.001 and P less than 0.01) whereas practolol and IPS 339 [t-butyl-amino-3 ol-2 propyl) oximino-9 fluorene] had little effect. 2 A positive correlation was shown between the degree of inhibition of renin release and the pA2 of the antagonists at the beta1-adrenoceptors. 4 When practolol and IPS 339 were used in equipotent molar concentrations to propranolol for the beta1-adrenoceptors they inhibited renin release. 5 The results suggest that the adrenoceptor involved in the renin release induced by isoprenaline in the rat kidney is of the beta1-type.

Adrenergic beta-Antagonists↗

PubMed1985

A search for selective antagonists at M2 muscarinic receptors.

Isolated preparations of guinea-pig ileum and atria have been used to estimate the dose-ratios produced by antagonists at muscarinic receptors. Experiments with 4-diphenyl-acetoxy-N-methylpiperidine (4DAMP) metho-salts and with its isomer, 3DAMP methiodide, indicate that these are only slightly affected by the choice of physiological salt solution, the choice of agonist and the presence or absence of hexamethonium. Methyl or chloro groups in the p-position of the two benzene rings in 4DAMP metho-salts markedly reduce affinity and selectivity. When the two benzene rings are linked together, as in the fluorene-9-carboxylic ester, the affinity for the receptors in the atria is comparable with that of 4DAMP methobromide but that for the ileum is about half, so the selectivity is reduced. When the rings are linked as in the xanthene-9-carboxylic ester, the affinity for receptors in both tissues is greater than that of 4DAMP methobromide but there is less selectivity. When two molecules of 4DAMP are linked together by a polymethylene chain of from 4 to 12 carbon atoms the effects on affinity for muscarinic receptors in the guinea-pig ileum are different from those on affinity for muscarinic receptors in guinea-pig atria. The pentamethylene compound is the most selective: compared with 4DAMP methobromide it has slightly less affinity for receptors in the ileum but much less affinity for receptors in the atria. The effects of the compounds in antagonizing the actions of carbachol on atrial rate are not markedly different from their effects in antagonizing its actions on the force of the atrial contractions.

Animals↗

PubMed1996

Lysosomal storage of sulphated glycosaminoglycans induced by dicationic amphiphilic drug molecules: significance of the central planar ring system.

The immunomodulatory drug tilorone (2,7-bis[2-(diethylamino)ethoxy]fluoren-9-one) and several congeners are known to disturb the lysosomal degradation of sulphated glycosaminoglycans and thereby induce lysosomal storage of glycosaminoglycans in cultured cells and intact organisms. The molecules of tilorone and congeners consist of a planar aromatic ring system symmetrically substituted with two aliphatic side chains each carrying a protonizable nitrogen. In a previous study it was proposed that non-degradable glycosaminoglycan-drug complexes are formed by electrostatic interactions and that additionally intermolecular interactions between the drug molecules due to electronic coupling of their central planar ring system are important for formation and stabilization of the glycosaminoglycan-drug complexes and thus for the drug side effect in question. The significance of the central planar ring system was tested in the present study by comparing tilorone and the compound bis(beta-diethylamino-ethylether)hexestrol (DH) with respect to their potencies to cause lysosomal glycosaminoglycan storage in cultured bovine corneal fibroblasts. DH has the same side chains as tilorone, but its central apolar moiety lacks planarity. At a concentration (1.75 muM) which did not cause enhanced secretion of the lysosomal enzyme beta-hexosaminidase (E.C. 3.2.1.52), DH was significantly less potent than tilorone in causing storage of [35S]glycosaminoglycans. This is taken as support of the hypothesis that the planar tricyclic ring system is essential for the high potency of tilorone and its congeners to exert this adverse action.

Adjuvants, Immunologic↗

PubMed1994

Cloning and analysis of the genes for polycyclic aromatic hydrocarbon degradation.

Bacterial degradation of polycyclic aromatic hydrocarbons initially proceeds through monooxygenase or dioxygenase attack on the aromatic ring. The dihydroxylated compounds formed are substrates for ring cleavage and further catabolism to tricarboxylic acid cycle intermediates. A number of microbial strains, both gram positive and gram negative, have been isolated that have the metabolic capability to degrade polycyclic aromatic hydrocarbons to carbon dioxide and water. In addition, many of these strains have the ability to cometabolize structurally similar aromatic compounds that may not normally serve as metabolic inducers or as carbon sources. The genes from several of these strains have been cloned for the purpose of analyzing in more detail their structure and function. The cloned genes were used to determine the range of substrates that can be metabolized by the genetically encoded pathway. For instance, the cloned genes from Pseudomonas sp. XPW-2 placed in E. coli encoded for the oxidation of such polycyclic aromatic hydrocarbons as naphthalene, biphenyl, anthracene, phenanthrene, acenaphthylene, fluorene, fluoranthene, chrysene, and pyrene. The cloned genes were also used as genetic probes to determine the degree of homology, if any, there is between different microbial strains capable of degrading polycyclic aromatic hydrocarbons. These experiments indicated significant homology among the class of terrestrial naphthalene and phenanthrene-degrading strains. Nevertheless, little homology was seen across species lines or among strains capable of degrading higher molecular weight polycyclic aromatic hydrocarbons. This indicates that there is a diversity of genetically distinct pathways for polycyclic aromatic hydrocarbon degradation.

Alcohol Oxidoreductases↗