Tetrabromohydroquinone and riboflavin are possibly responsible for green luminescence in the luminous acorn worm, Ptychodera flava.

2,3,5,6-Tetrabromohydroquinone was isolated as a luminous substance from Ptychodera flava. This compound emitted light after addition of hydrogen peroxide under basic conditions. Since hydroquinone had no fluorescence, further investigation by spectral analysis revealed that riboflavin was the only possible light emitter having green fluorescence. In the presence of both tetrabromohydroquinone and riboflavin under a basic condition containing 70% 1,4-dioxane, green light emission was observed following the addition of hydrogen peroxide. We succeeded in recording the same emission spectrum as that in the bioluminescence caused by the addition of aqueous diluted hydrogen peroxide solution in P. flava.     

Three classes of ubiquinone analogs regulate the mitochondrial permeability transition pore through a common site

To identify the structural features required for regulation of the mitochondrial permeability transition pore (PTP) by ubiquinone analogs (Fontaine, E., Ichas, F., and Bernardi, P. (1998) J. Biol. Chem. 40, 25734-25740), we have carried out an analysis with quinone structural variants. We show that three functional classes can be defined: (i) PTP inhibitors (ubiquinone 0, decylubiquinone, ubiquinone 10, 2,3-dimethyl-6-decyl-1,4-benzoquinone, and 2,3,5-trimethyl-6-geranyl-1,4-benzoquinone); (ii) PTP inducers (2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1,4-benzoquinone and 2,5-dihydroxy-6-undecyl-1,4-benzoquinone); and (iii) PTP-inactive quinones that counteract the effects of both inhibitors and inducers (ubiquinone 5 and 2,3,5-trimethyl-6-(3-hydroxyisoamyl)-1,4-benzoquinone) . The structure-function correlation indicates that minor modifications in the isoprenoid side chain can turn an inhibitor into an activator, and that the methoxy groups are not essential for the effects of quinones on the PTP. Since the ubiquinone analogs used in this study have a similar midpoint potential and decrease mitochondrial production of reactive oxygen species to the same extent, these results support the hypothesis that quinones modulate the PTP through a common binding site rather than through oxidation-reduction reactions. Occupancy of this site can modulate the PTP open-closed transitions, possibly through secondary changes of the PTP Ca(2+) binding affinity.     

Cleavage and synthesis function of high and low redox potential laccases towards 4-morpholinoaniline and aminated as well as chlorinated phenols

Laccases are able to mediate both cleavage and synthesis processes. The basis for this dual reaction capability lies in the property of the enzyme laccase to oxidize phenolic, and to some extent non-phenolic substances, to reactive radicals which can undergo on the one hand separations of small substitutents or large molecule parts from the parent compound and on the other hand coupling reactions with other radicals or molecules which are not themselves oxidizable by laccase. The cleavage of the non-phenolic compound 4-morpholinoaniline as well as the deamination of 4-aminophenol and the dechlorination of 4-chlorophenol resulted in the formation of 1,4-hydroquinone which is immediately oxidized by laccase to 1,4-benzoquinone. The formation of the 1,4-hydroquinone/1,4-benzoquinone is the rate limiting step for the synthesis of the heteromolecular dimers and trimers composed of 1,4-benzoquinone and one or two molecules of morpholine. In addition to the synthesis of new compounds from the cleavage products, 4-morpholinoaniline polymerized probably via azo groups and C-N bonds to a homomolecular dimer and trimer. Similarities and differences in cleavage and synthesis reactions catalyzed by the low redox potential laccase of Myceliophthora thermophila (0.46 V) and the high redox potential laccase of Pycnoporus cinnabarinus (0.79 V) were determined. In addition, the dependency of the cleavage and synthesis efficiencies on the (a) structure and redox potential of the laccase, (b) structure and redox potential of the substrate, (c) pH value of the buffer used, (d) incubation temperature, (e) solvent concentration, and (f) laccase activity is discussed in general.     

Degradation of orcinol by Aspergillus niger

Aspergillus niger could utilize orcinol (5-methyl-resorcinol or 3,5-dihydroxytoluene) as the sole source of carbon and energy. In the first step of catabolism A. niger hydroxylates orcinol to form 2,3,5-trihydroxytoluene. Its oxidized form, 2-hydroxy-6-methyl-1,4-benzoquinone, was also formed in the culture medium during growth of this organism. Orcinol-grown cells showed a net increase in the intracellular acetate pool, compared with glucose-grown cells. Cell-free extracts of orcinol-grown cells showed higher activity of orcinol hydroxylase, catechol 1,2-oxygenase, and isocitrate lyase than that of glucose-grown cells. Both orcinol-grown and resorcinol-grown cells exhibit similar respiratory activity on all the substrates checked.     

Group B sox genes that contribute to specification of the vertebrate brain are expressed in the apical organ and ciliary bands of hemichordate larvae

We have identified and characterized the sequence and expression of two Group B Sox genes in the acorn worm, Ptychodera flava. One sequence represents a Group B1 Sox gene and is designated Pf-SoxB1; the other is a Group B2 Sox gene and is designated Pf-SoxB2. Both genes encode polypeptides with an HMG domain in the N-terminal half. Whole-mount in situ hybridization to embryonic and larval stages of P. flava shows that the two genes are expressed in rather similar patterns at these stages. Expression is first detected in the cells of the blastula and subsequently localizes to the ectoderm during gastrulation. As the mouth forms, expression becomes concentrated in the stomodeum region. During morphogenesis of the tornaria larva, expression in the stomodeal ectoderm remains prominent around the mouth and under the oral hood. Later the genes are prominently upregulated in the ciliary bands and the apical organ. These results provide additional evidence that genes playing essential roles in the formation of the chordate dorsal central nervous system function in the development of the ciliary bands and apical organ, neural structures of this non-chordate deuterostome larva.     

Study of the protein-ubiquinone interaction in succinate-cytochrome C reductase with azido-ubiquinone derivatives

Several azido-ubiquinones have been synthesized for the study of protein-ubiquinone interaction in succinate-cytochrome $\text{c}$ reductase. In the absence of light, azido-ubiquinones are partially effective in restoring enzymatic activity to ubiquinone- and phospholipid-depleted reductase and the binding of azido-ubiquinones can be partially reversed by 5-(10-bromodecyl)-ubiquinone. When 2-azido-3-methoxy-5-geranyl-6-methyl-1,4-benzoquinone reactivated reductase is illuminated with long wavelength UV light, a complete and irreversible inhibition is observed. This specific photo-inactivation, exerted only by 2-azido-3-methoxy-5-geranyl-6-methyl-1,4-benzoquinone, and not by other azido-ubiquinone derivatives, is evidence for the existence of a specific benzoquinone ring binding site in the enzyme.     

Metabolism of resorcinylic compounds by bacteria: orcinol pathway in Pseudomonas putida.

Enrichment cultures yielded two strains of Pseudomonas putida capable of growth with orcinol (3,5-dihydroxytoluene) as the sole source of carbon. Experiments with cell suspensions and cell extracts indicate that orcinol is metabolized by hydroxylation of the benzene ring followed successively by ring cleavage and hydrolyses to give 2 mol of acetate and 1 mol of pyruvate per mol of orcinol as shown: orcinol leads to 2,3,5-trihydroxytoluene leads to 2,4,6-trioxoheptanoate leads to acetate + acetylpyruvate leads to acetate + pyruvate. Evidence for this pathway is based on: (i) high respiratory activities of orcinol-grown cells towards 2,3,5-trihydroxytoluene; (ii) transient accumulation of a quinone, probably 2-hydroxy-6-methyl-1,4-benzoquinone, during grouth with orcinol; (iii) formation of pyruvate and acetate from orcinol, 2,3,5-trihydroxytoluene, and acetylpyruvate catalyzed by extracts of orcinol, but not by succinate-grown cells; (iv) characterization of the product of oxidation of 3-methylcatechol (an analogue of 2,3,5-trihydroxytoluene) showing that oxygenative cleavage occurs between carbons bearing methyl and hydroxyl substituents; (v) transient appearance of a compound having spectral properties similar to those of acetylpyruvate during 2,3,5-trihydroxytoluene oxidation by extracts of orcinol-grown cells. Orcinol hydroxylase exhibits catalytic activity when resorcinol or m-cresol is substituted for orcinol; hydroxyquinol and 3-methylcatechol are substrates for the ring cleavage enzyme 2,3,5-trihydroxytoluene-1,2-oxygenase. The enzymes of this pathway are induced by growth with orcinol but not with glucose or succinate.     

Bioluminescence characteristics of Lake Shira water

Bioluminescence bioassays based on luminous bacteria (Photobacterium phosphopreum) and coupled enzyme system NADH-FMN-oxidoreductase-luciferase were adapted for monitoring the saline-water conditions of Lake Shira (Khakasia, Siberia). The differences in bioluminescence responses have been found to be related to the salt composition and the oxidation-reduction properties of water. Bioluminescent kinetics parameters, which are mostly sensitive to pollution under conditions of saline water, have been observed. The enzymatic system in the presence of 1,4-benzoquinone are shown to be more sensitive to redox characteristics of the salt water than this in the absence of 1,4-benzoquinone. 1,4-benzoquinone should be applied for the preparation of a model solution for the monitoring of redox properties of the salt water. Using this technique, the results of bioluminescence analysis are used to construct a heterogeneity map that characterizes the spatial and temporal water quality of lake Shira. A partial map was based on the bioluminescence characteristics of water samples taken along the shoreline, sampling stations in the different places and in different depths of the lake. It has been demonstrated that the bioluminescence assay measurements must be done within two hours after the sampling time.     

Newbouldiaquinone A: A naphthoquinone-anthraquinone ether coupled pigment, as a potential antimicrobial and antimalarial agent from Newbouldia laevis

The study of the chemical constituents of the roots of Newbouldia laevis (Bignoniaceae) has resulted in the isolation and characterization of a naphthoquinone-anthraquinone coupled pigment named newbouldiaquinone A (1) together with 14 known compounds: apigenin, chrysoeriol, newbouldiaquinone, lapachol, 2-methylanthraquinone, 2-acetylfuro-1,4-naphthoquinone, 2,3-dimethoxy-1,4-benzoquinone, oleanolic acid, canthic acid, 2-(4-hydroxyphenyl)ethyl triacontanoate, newbouldiamide, 5,7-dihydroxydehydroiso-alpha-lapachone, beta-sitosterol, and beta-sitosterol glucopyranoside. The structure elucidation of the isolated compounds was established based on spectroscopic studies, notably of the 2D NMR spectra. The antimalarial activity of compound (1) against Plasmodium falciparum in vitro shows moderate chemo suppression of parasitic growth. Its antimicrobial activity against a wide range of microorganisms was 13- and 24-fold more active against Candida gabrata and Enterobacter aerogens than the reference antibiotics nystatin and gentamycin.     

Purification and characterization of an intracellular NADH: quinone reductase from Trametes versicolor

Intracellular NADH:quinone reductase involved in degradation of aromatic compounds including lignin was purified and characterized from white rot fungus Trametes versicolor. The activity of quinone reductase was maximal after 3 days of incubation in fungal culture, and the enzyme was purified to homogeneity using ion-exchange, hydrophobic interaction, and gel filtration chromatographies. The purified enzyme has a molecular mass of 41 kDa as determined by SDS-PAGE, and exhibits a broad temperature optimum between 20-40 degrees C , with a pH optimum of 6.0. The enzyme preferred FAD as a cofactor and NADH rather than NADPH as an electron donor. Among quinone compounds tested as substrate, menadione showed the highest enzyme activity followed by 1,4-benzoquinone. The enzyme activity was inhibited by CuSO(4), HgCl(2), MgSO(4), MnSO(4), AgNO(3), dicumarol, KCN, NaN(3), and EDTA. Its Km and Vmax with NADH as an electron donor were 23 microM and 101 mM/mg per min, respectively, and showed a high substrate affinity. Purified quinone reductase could reduce 1,4-benzoquinone to hydroquinone, and induction of this enzyme was higher by 1,4-benzoquinone than those of other quinone compounds.     

Quinone-induced inhibition of urease: elucidation of its mechanisms by probing thiol groups of the enzyme

In this work we studied the reaction of four quinones, 1,4-benzoquinone (1,4-BQ), 2,5-dimethyl-1,4-benzoquinone (2,5-DM-1,4-BQ), tetrachloro-1,4-benzoquinone (TC-1,4-BQ) and 1,4-naphthoquinone (1,4-NQ) with jack bean urease in phosphate buffer, pH 7.8. The enzyme was allowed to react with different concentrations of the quinones during different incubation times in aerobic conditions. Upon incubation the samples had their residual activities assayed and their thiol content titrated. The titration carried out with use of 5,5'-di-thiobis(2-nitrobenzoic) acid was done to examine the involvement of urease thiol groups in the quinone-induced inhibition. The quinones under investigation showed two distinct patterns of behaviour, one by 1,4-BQ, 2,5-DM-1,4-BQ and TC-1,4-BQ, and the other by 1,4-NQ. The former consisted of a concentration-dependent inactivation of urease where the enzyme-inhibitor equilibrium was achieved in no longer than 10min, and of the residual activity of the enzyme being linearly correlated with the number of modified thiols in urease. We concluded that arylation of the thiols in urease by these quinones resulting in conformational changes in the enzyme molecule is responsible for the inhibition. The other pattern of behaviour observed for 1,4-NQ consisted of time- and concentration-dependent inactivation of urease with a nonlinear residual activity-modified thiols dependence. This suggests that in 1,4-NQ inhibition, in addition to the arylation of thiols, operative are other reactions, most likely oxidations of thiols provoked by 1,4-NQ-catalyzed redox cycling. In terms of the inhibitory strength, the quinones studied formed a series: 1,4-NQ approximately 2,5-DM-1,4-BQ<1,4-BQ相似文献   

Insulinotropic effect of the tumor promoter teleocidin in isolated pancreatic islets

A tumor promoter teleocidin induced insulin secretion from isolated pancreatic islets in a concentration-dependent manner. The teleocidin-induced secretion was inhibited by p-bromophenacyl bromide, nordihydroguaiaretic acid, 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline and 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone, but not by indomethacin. Insulinotropic concentrations of teleocidin stimulated 6-keto-prostaglandin F1 alpha release from pancreatic islets. These results suggest that phospholipase A2 activation and lipoxygenase product(s) are involved in the mechanism of teleocidin-induced insulin secretion.     

Metabolites of 2-aminophenol from fruit bodies of Lepiota americana (Agaricales)

From the acetone extract of the North American toadstool Lepiota americana 2-aminophenoxazin-3-one (1) and a novel amino-1,4-benzoquinone derivative, lepiotaquinone (2), were isolated. The structure of 2 was confirmed by its preparation from 2-aminophenol and amino-1,4-benzoquinone.     

A Salmonella typhimurium mutant dependent upon carbamyl aspartate for resistance to 5-fluorouracil is specifically affected in ubiquinone biosynthesis.

The isolation and properties of a mutant dependent upon exogenous carbamyl aspartate for resistance to 5-fluorouracil are described. The mutant was deficient in the synthesis of ubiquinone and accumulated a quinone provisionally identified as the ubiquinone precursor 2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone. The mutation resulted in an alteration in the regulation of synthesis of enzymes involved in de novo pyrimidine biosynthesis but did not establish a functional block in dihydroorotate dehydrogenase activity in vivo. Conditional resistance to 5-fluorouracil apparently occurred through an inhibition of the conversion of the analog to the nucleotide level.     

Isolation and identification of secondary metabolites of a strain ofAspergillus terreus,a common food contaminant

2-Hydroxy 3-methyl 1,4-benzoquinone 5,6 epoxide was identified as secondary metabolite of a strain ofAspergillus terreus, a common contaminant of animal feeds. In addition, the following compounds were also tentatively identified to be produced by this organism: 2-hYdroxy 3-methyl 1,4-benzoquinone; 2-methyl 1,4-benzoquinone 5,6-epoxide; naphthazarin epoxide; and 2-hydroxy 3-methyl 1,4-benzoquinone 5, 6-epoxide.     

Fe-superoxide dismutase and 2-hydroxy-1,4-benzoquinone reductase preclude the auto-oxidation step in 4-aminophenol metabolism by <Emphasis Type="Italic">Burkholderia</Emphasis> sp. strain AK-5

Burkholderia sp. strain AK-5 converts 4-aminophenol to maleylacetic acid via 1,2,4-trihydroxybenzene, which is unstable in vitro and non-enzymatically auto-oxidized to 2-hydroxy-1,4-benzoquinone. Crude extract of strain AK-5 retarded the auto-oxidation and reduced the substrate analogue, 2,6-dimethoxy-1,4-benzoquinone, in the presence of NADH. The two enzymes responsible were purified to homogeneity. The deduced amino acid sequence of the enzyme that inhibited the auto-oxidation showed a high level of identity to sequences of iron-containing superoxide dismutases (Fe-SODs) and contained a conserved metal-ion-binding site; the purified enzyme showed superoxide dismutase activity and contained 1 mol of Fe per mol of enzyme, identifying it as Fe-SOD. Among three type SODs tested, Fe-SOD purified here inhibited the auto-oxidation most efficiently. The other purified enzyme showed a broad substrate specificity toward benzoquinones, including 2-hydroxy-1,4-benzoquinone, converting them to the corresponding 1,4-benzenediols; the enzyme was identified as 2-hydroxy-1,4-benzoquinone reductase. The deduced amino acid sequence did not show a high level of identity to that of benzoquinone reductases from bacteria and fungi that degrade chlorinated phenols or nitrophenols. The indirect role of Fe-SOD in 1,2,4-trihydroxybenzene metabolism is probably to scavenge and detoxify reactive species that promote the auto-oxidation of 1,2,4-trihydroxybenzene in vivo. The direct role of benzoquinone reductase would be to convert the auto-oxidation product back to 1,2,4-trihydroxybenzene. These two enzymes together with 1,2,4-trihydroxybenzene 1,2-dioxygenase convert 1,2,4-trihydroxybenzene to maleylacetic acid.     

11β-Hydroxysteroid dehydrogenase-type 2 evolved from an ancestral 17β-Hydroxysteroid dehydrogenase-type 2

11β-Hydroxysteroid dehydrogenase-type 2 (11β-HSD2) regulates the local concentration of cortisol that can activate the glucocorticoid receptor and mineralocorticoid receptor, as well as the concentration of 11-keto-testosterone, the active androgen in fish. Similarly, 17β-HSD2 regulates the levels of testosterone and estradiol that activate the androgen receptor and estrogen receptor, respectively. Interestingly, although human 11β-HSD2 and 17β-HSD2 act at different positions on different steroids, these enzymes are paralogs. Despite the physiological importance of 11β-HSD2 and 17β-HSD2, details of their origins and divergence from a common ancestor are not known. An opportunity to understand their evolution is presented by the recent sequencing of genomes from sea urchin, a basal deuterostome, and amphioxus, a basal chordate, and the availability of substantial sequence for acorn worm and elephant shark, which together provide a more complete dataset for analysis of the origins of 11β-HSD2 and 17β-HSD2. BLAST searches find an ancestral sequence of 17β-HSD2 in sea urchin, acorn worm and amphioxus, while an ancestral sequence of 11β-HSD2 first appears in sharks. Sequence analyses indicate that 17β-HSD2 in sea urchin may have a non-enzymatic activity. Evolutionary analyses indicate that if acorn worm 17β-HSD2 is catalytically active, then it metabolizes novel substrate(s).     

Characterization and Genetic Analysis of Mutant Strains of Escherichia coli K-12 Accumulating the Ubiquinone Precursors 2-Octaprenyl-6-Methoxy-1,4-Benzoquinone and 2-Octaprenyl-3-Methyl-6-Methoxy-1,4-Benzoquinone

The ubiquinone precursors, 2-octaprenyl-6-methoxy-1,4-benzoquinone and 2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone, were isolated from ubiquinone-deficient mutants of Escherichia coli and identified by nuclear magnetic resonance and mass spectrometry. Mutants accumulating 2-octaprenyl-6-methoxy-1,4-benzoquinone and 2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone were shown to carry mutations in genes designated ubiE and ubiF, respectively. The ubiE gene was shown to be cotransducible with metE (minute 75) and close to two other genes concerned with ubiquinone biosynthesis. The ubiF gene was located close to minute 16 by cotransduction with the lip, gltA, and entA genes.     

Development and neural organization of the tornaria larva of the Hawaiian hemichordate, Ptychodera flava

We report scanning and transmission electron microscopic studies of the early development of the Hawaiian acorn worm, Ptychodera flava. In addition, we provide an immunohistochemical identification of the larval nervous system. Development occurs and is constrained within the stout chorion and fertilization envelope that forms upon the release of the cortical granules in the cytoplasm of the egg. The blastula consists of tall columnar blastomeres encircling a small blastocoel. Typical gastrulation occurs and a definitive tornaria is formed compressed within the fertilization envelope. The young tornaria hatches at 44 hr and begins to expand. The major circumoral ciliary band that crosses the dorsal surface and passes preorally and postorally is well developed. In addition, we find a nascent telotroch, as well as a midventral ciliary band that is already clearly developed. The epithelium of tornaria is a mosaic of monociliated and multiciliated cells. Immunohistochemistry with a novel neural marker, monoclonal antibody 1E11, first detects nerve cells at the gastrula stage. In tornaria, 1E11 staining nerve cells occur throughout the length of the ciliary bands, in the apical organ, in a circle around the mouth, in the esophageal epithelium and in circumpylorus regions. Axon(s) and apical processes extend from the nerve cell bodies and run in tracks along the ciliary bands. Axons extending from the preoral and postoral bands extend into the oral field and form a network. The tornaria nervous system with ciliary bands and an apical organ is rather similar to the echinoderm bipinnaria larvae.