共查询到20条相似文献,搜索用时 46 毫秒
1.
Xiao Y Wu JF Liu H Wang SJ Liu SJ Zhou NY 《Applied microbiology and biotechnology》2006,73(1):166-171
The genes encoding enzymes involved in the initial reactions during degradation of 4-chloronitrobenzene (4CNB) were characterized from the 4CNB utilizer Pseudomonas
putida ZWL73, in which a partial reductive pathway was adopted. A DNA fragment containing genes coding for chloronitrobenzene nitroreductase (CnbA) and hydroxylaminobenzene mutase (CnbB) were PCR-amplified and subsequently sequenced. These two genes were actively expressed in Escherichia
coli, and recombinant E. coli cells catalyzed the conversion of 4CNB to 2-amino-5-chlorophenol, which is the ring-cleavage substrate in the degradation of 4CNB. Phylogenetic analyses on sequences of chloronitrobenzene nitroreductase and hydroxylaminobenzene mutase revealed that these two enzymes are closely related to the functionally identified nitrobenzene nitroreductase and hydroxylaminobenzene mutase from Pseudomonas strains JS45 and HS12. The nitroreductase from strain ZWL73 showed a higher specific activity toward 4CNB than nitrobenzene (approximately at a ratio of 1.6:1 for the recombinant or 2:1 for the wild type), which is in contrast to the case where the nitroreductase from nitrobenzene utilizers Pseudomonas
pseudoalcaligenes JS45 with an apparently lower specific activity against 4CNB than nitrobenzene (0.16:1) [Kadiyala et al. Appl Environ Microbiol 69:6520–6526, 2003]. This suggests that the nitroreductase from 4-chloronitrobenzene utilizer P. putida ZWL73 may have evolved to prefer chloronitrobenzene to nitrobenzene as its substrate.Y.X. and J.-F.W. equally contributed to this work. 相似文献
2.
Construction of Escherichia coli strains for conversion of nitroacetophenones to ortho-aminophenols 总被引:1,自引:0,他引:1
The predominant bacterial pathway for nitrobenzene (NB) degradation uses an NB nitroreductase and hydroxylaminobenzene (HAB) mutase to form the ring-fission substrate ortho-aminophenol. We tested the hypothesis that constructed strains might accumulate the aminophenols from nitroacetophenones and other nitroaromatic compounds. We constructed a recombinant plasmid carrying NB nitroreductase (nbzA) and HAB mutase A (habA) genes, both from Pseudomonas pseudoalcaligenes JS45, and expressed the enzymes in Escherichia coli JS995. IPTG (isopropyl-beta-D-thiogalactopyranoside)-induced cells of strain JS995 rapidly and stoichiometrically converted NB to 2-aminophenol, 2-nitroacetophenone (2NAP) to 2-amino-3-hydroxyacetophenone (2AHAP), and 3-nitroacetophenone (3NAP) to 3-amino-2-hydroxyacetophenone (3AHAP). We constructed another recombinant plasmid containing the nitroreductase gene (nfs1) from Enterobacter cloacae and habA from strain JS45 and expressed the enzymes in E. coli JS996. Strain JS996 converted NB to 2-aminophenol, 2-nitrotoluene to 2-amino-3-methylphenol, 3-nitrotoluene to 2-amino-4-methylphenol, 4-nitrobiphenyl ether to 4-amino-5-phenoxyphenol, and 1-nitronaphthalene to 2-amino-1-naphthol. In larger-scale biotransformations catalyzed by strain JS995, 75% of the 2NAP transformed was converted to 2AHAP, whereas 3AHAP was produced stoichiometrically from 3NAP. The final yields of the aminophenols after extraction and recovery were >64%. The biocatalytic synthesis of ortho-aminophenols from nitroacetophenones suggests that strain JS995 may be useful in the biocatalytic production of a variety of substituted ortho-aminophenols from the corresponding nitroaromatic compounds. 相似文献
3.
Bacterial Conversion of Hydroxylamino Aromatic Compounds by both Lyase and Mutase Enzymes Involves Intramolecular Transfer of Hydroxyl Groups
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hydroxylamino aromatic compounds are converted to either the corresponding aminophenols or protocatechuate during the bacterial degradation of nitroaromatic compounds. The origin of the hydroxyl group of the products could be the substrate itself (intramolecular transfer mechanism) or the solvent water (intermolecular transfer mechanism). The conversion of hydroxylaminobenzene to 2-aminophenol catalyzed by a mutase from Pseudomonas pseudoalcaligenes JS45 proceeds by an intramolecular hydroxyl transfer. The conversions of hydroxylaminobenzene to 2- and 4-aminophenol by a mutase from Ralstonia eutropha JMP134 and to 4-hydroxylaminobenzoate to protocatechuate by a lyase from Comamonas acidovorans NBA-10 and Pseudomonas sp. strain 4NT were proposed, but not experimentally proved, to proceed by the intermolecular transfer mechanism. GC-MS analysis of the reaction products formed in H218O did not indicate any 18O-label incorporation during the conversion of hydroxylaminobenzene to 2- and 4-aminophenols catalyzed by the mutase from R. eutropha JMP134. During the conversion of 4-hydroxylaminobenzoate catalyzed by the hydroxylaminolyase from Pseudomonas sp. strain 4NT, only one of the two hydroxyl groups in the product, protocatechuate, was 18O labeled. The other hydroxyl group in the product must have come from the substrate. The mutase in strain JS45 converted 4-hydroxylaminobenzoate to 4-amino-3-hydroxybenzoate, and the lyase in Pseudomonas strain 4NT converted hydroxylaminobenzene to aniline and 2-aminophenol but not to catechol. The results indicate that all three types of enzyme-catalyzed rearrangements of hydroxylamino aromatic compounds proceed via intramolecular transfer of hydroxyl groups. 相似文献
4.
Hydroxylamino aromatic compounds are converted to either the corresponding aminophenols or protocatechuate during the bacterial degradation of nitroaromatic compounds. The origin of the hydroxyl group of the products could be the substrate itself (intramolecular transfer mechanism) or the solvent water (intermolecular transfer mechanism). The conversion of hydroxylaminobenzene to 2-aminophenol catalyzed by a mutase from Pseudomonas pseudoalcaligenes JS45 proceeds by an intramolecular hydroxyl transfer. The conversions of hydroxylaminobenzene to 2- and 4-aminophenol by a mutase from Ralstonia eutropha JMP134 and to 4-hydroxylaminobenzoate to protocatechuate by a lyase from Comamonas acidovorans NBA-10 and Pseudomonas sp. strain 4NT were proposed, but not experimentally proved, to proceed by the intermolecular transfer mechanism. GC-MS analysis of the reaction products formed in H(2)(18)O did not indicate any (18)O-label incorporation during the conversion of hydroxylaminobenzene to 2- and 4-aminophenols catalyzed by the mutase from R. eutropha JMP134. During the conversion of 4-hydroxylaminobenzoate catalyzed by the hydroxylaminolyase from Pseudomonas sp. strain 4NT, only one of the two hydroxyl groups in the product, protocatechuate, was (18)O labeled. The other hydroxyl group in the product must have come from the substrate. The mutase in strain JS45 converted 4-hydroxylaminobenzoate to 4-amino-3-hydroxybenzoate, and the lyase in Pseudomonas strain 4NT converted hydroxylaminobenzene to aniline and 2-aminophenol but not to catechol. The results indicate that all three types of enzyme-catalyzed rearrangements of hydroxylamino aromatic compounds proceed via intramolecular transfer of hydroxyl groups. 相似文献
5.
Hydroxylaminobenzene mutase is the enzyme that converts intermediates formed during initial steps in the degradation of nitrobenzene to a novel ring-fission lower pathway in Pseudomonas pseudoalcaligenes JS45. The mutase catalyzes a rearrangement of hydroxylaminobenzene to 2-aminophenol. The mechanism of the reactions and the properties of the enzymes are unknown. In crude extracts, the hydroxylaminobenzene mutase was stable at SDS concentrations as high as 2%. A procedure including Hitrap-SP, Hitrap-Q and Cu(II)-chelating chromatography was used to partially purify the enzyme from an Escherichia coli clone. The partially purified enzyme was eluted in the void volume of a Superose-12 gel-filtration column even in the presence of 0.05% SDS in 25 mM Tris/HCl buffer, which indicated that it was highly associated. When the enzymatic conversion of hydroxylaminobenzene to 2-aminophenol was carried out in 18O-labeled water, the product did not contain 18O, as determined by GC-MS. The results indicate that the reaction proceeded by intramolecular transfer of the hydroxy group from the nitrogen to the C-2 position of the ring. The mechanism is clearly different from the intermolecular transfer of the hydroxy group in the non-enzymatic Bamberger rearrangement of hydroxylaminobenzene to 4-aminophenol and in the enzymatic hydroxymutation of chorismate to isochorismate. 相似文献
6.
Picolinic acids have been synthesized previously from catechols by the action of catechol 2,3-dioxygenase and a subsequent
chemical reaction in the presence of ammonia. 2-Aminophenol 1,6-dioxygenase catalyzes ring cleavage of several ortho-aminophenols. The ring fission products spontaneously convert to picolinic acids. Resting cells of Escherichia coli DH5α/pNBZ14 harboring the genes for 2-aminophenol 1,6-dioxygenase converted 2-aminophenol and 6-amino-m-cresol to picolinic acid and 5-methylpicolinic acid with yields greater than 90%. The results provide a convenient strategy
for the synthesis of substituted picolinic acids from the corresponding aminophenols. Journal of Industrial Microbiology & Biotechnology (2000) 25, 25–28.
Received 25 October 1999/ Accepted in revised form 19 April 2000 相似文献
7.
Yuanyuan Qu Hao Zhou Ang Li Fang Ma Jiti Zhou 《Applied microbiology and biotechnology》2011,89(3):655-663
Ferredoxin reductase BphA4 was well known as a component of biphenyl dioxygenase. However, there was little information about
whether it could utilize nonphysiological oxidants as electron acceptors. In the present study, we reported the novel nitroreductase
activity of BphA4LA−4. The homology model of ferredoxin reductase BphA4 from Dyella ginsengisoli LA−4 was constructed. According to the alignment of three-dimensional structures, it was supposed that BphA4LA−4 could function as nitroreductase. Recombinant His-tagged BphA4LA−4 was purified with a molecular mass of 49.6 ± 1 kDa. Biochemical characterization of purified BphA4LA−4 possessed the nitroreductase activity with the optimal temperature 50°C and pH 8.0. The substrate spectrum and kinetics indicated
BphA4LA−4 could reduce several nitroaromatics with different apparent K
m values: m-dinitrobenzene (560 μM), o-dinitrobenzene (1,060 μM), o-nitroaniline (1,570 μM), m-nitrobenzoic acid (1,300 μM) and m-nitrophenol (67 μM). The nitroreductase activity was further explained by docking studies, which was indicated that Arg 288
should play an important role in binding nitroaromatics. Moreover, there existed a good linear correlation between lnK
m and calculated binding energy. 相似文献
8.
Three NAD(P)H-dependent nitroreductases that can transform 2,4,6-trinitrotoluene (TNT) by two reduction pathways were detected
in Klebsiella sp. C1. Among these enzymes, the protein with the highest reduction activity of TNT (nitroreductase I) was purified to homogeneity
using ion-exchange, hydrophobic interaction, and size exclusion chromatographies. Nitroreductase I has a molecular mass of
27 kDa as determined by SDS-PAGE, and exhibits a broad pH optimum between 5.5 and 6.5, with a temperature optimum of 30–40°C.
Flavin mononucleotide is most likely the natural flavin cofactor of this enzyme. The N-terminal amino acid sequence of this
enzyme does not show a high degree of sequence similarity with nitroreductases from other enteric bacteria. This enzyme catalyzed
the two-electron reduction of several nitroaromatic compounds with very high specific activities of NADPH oxidation. In the
enzymatic transformation of TNT, 2-amino-4,6-dinitrotoluene and 2,2′,6,6′-tetranitro-4,4′-azoxytoluene were detected as transformation
products. Although this bacterium utilizes the direct ring reduction and subsequent denitration pathway together with a nitro
group reduction pathway, metabolites in direct ring reduction of TNT could not easily be detected. Unlike other nitroreductases,
nitroreductase I was able to transform hydroxylaminodinitrotoluenes (HADNT) into aminodinitrotoluenes (ADNT), and could reduce
ortho isomers (2-HADNT and 2-ADNT) more easily than their para isomers (4-HADNT and 4-ADNT). Only the nitro group in the ortho position of 2,4-DNT was reduced to produce 2-hydroxylamino-4-nitrotoluene by nitroreductase I; the nitro group in the para position was not reduced. 相似文献
9.
Thermal inactivation of cherry leaf roll virus in tissue cultures of Nicotiana rustica raised from seeds and meristem-tips 总被引:1,自引:0,他引:1
Nicotiana rustica tissue cultures derived from seeds or embryos infected with cherry leaf roll virus (CLRV), remained infected after culture at 22 oC. No infectivity was found in cultures held at 32 oC for 5 days but it was readily detected after such cultures were transferred to 25 oC for 8 days. Virus was permanently eradicated from most plants after 20 days incubation at 32 oC and from all plants after 7 days incubation at 40 oC. Partially purified preparations of CLRV lost infectivity after 9–12 days at 22oC, 5 days at 32oC and 3 days at 40oC. 相似文献
10.
Burke PJ Wong LC Jenkins TC Knox RJ Stanforth SP 《Bioorganic & medicinal chemistry letters》2011,21(24):7447-7450
A series of 2-nitroaryl-1,2,3,4-tetrahydroisoquinolines 10 and nitro-substituted 5,6-dihydrobenzimidazo[2,1-a]isoquinoline N-oxides 11 have been synthesised and evaluated as potential bioreducible substrates for the enzymes NAD(P)H: quinone oxidoreductase 1 (NQO1) and Escherichia coli nitroreductase (NR). Also prepared and evaluated were 2-(3,5-dinitropyridin-2-yl)-1,2,3,4-tetrahydroisoquinoline 12 and 5,6-dihydro-10-nitropyrido[3″,2″:4′,5′]imidazo[2′,1′-a]isoquinoline 12-oxide 13. Both compounds 10b and 13 were reduced faster by human NQO1 than by CB-1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide]. 相似文献
11.
Jianyong Li Xueling Zhao Bruce M. Christensen 《Insect biochemistry and molecular biology》1994,24(10)
Phenol oxidase (PO) and dopachrome conversion enzyme (DCE) were partially purified from Aedes aegypti larvae by ammonium sulfate fractionation. PO from A. aegypti functions in the hydroxylation of monophenols (e.g., tyrosine and tyramine) to their related o-diphenols, and the oxidation of o-diphenols (e.g., l-dopa, dopamine, N-acetyldopamine) to their respective o-quinones. Partially purified DCE showed high specificity toward dopachrome generated from dopa with the l-configuration. The combined effects of PO and DCE significantly accelerated melanization pathways when l-dopa was used as substrate. Significant DCE activity also was detected in hemolymph samples from adult, female A. aegypti, and undoubtedly plays a role in melanotic encapsulation reactions. 相似文献
12.
巴氏杆菌(主要是多杀性巴氏杆菌)可以引起多种动物疫病(巴氏杆菌病),同时也引起人类感染发病。[目的] 研究巴氏杆菌糖酵解酶对宿主细胞(兔肾细胞)和两种常见分子[纤连蛋白(fibronectin,Fn)和血浆纤维蛋白溶解酶原(plasminogen,Plg)]的黏附作用。[方法] 采用原核表达系统对多杀性巴氏杆菌的糖酵解酶进行表达并纯化及制备多克隆抗体,通过菌体表面蛋白定位检测、黏附与黏附抑制等实验探究巴氏杆菌糖酵解酶的黏附作用。[结果] 菌体表面蛋白检测结果显示除烯醇化酶和丙酮酸激酶外的7个糖酵解酶在多杀性巴氏杆菌表面存在。这7个糖酵解酶均能黏附兔肾细胞,但仅有磷酸葡萄糖异构酶的多克隆抗体能对多杀性巴氏杆菌黏附宿主细胞产生抑制作用。Far Western blotting结果显示9个糖酵解酶均能结合宿主Fn和Plg。招募抑制实验结果显示磷酸葡萄糖异构酶、醛缩酶、磷酸甘油酸变位酶的抗体对多杀性巴氏杆菌结合Fn和Plg都有抑制作用,磷酸果糖激酶、丙糖磷酸异构酶、甘油醛-3-磷酸脱氢酶、磷酸甘油激酶抗体仅对多杀性巴氏杆菌结合Fn或Plg有抑制作用。[结论] 多杀性巴氏杆菌糖酵解酶成员葡萄糖异构酶、磷酸果糖激酶、醛缩酶、丙糖磷酸异构酶、甘油醛-3-磷酸脱氢酶、磷酸甘油激酶、磷酸甘油酸变位酶在多杀性巴氏杆菌黏附宿主细胞或分子过程中发挥作用。该研究的完成将加深巴氏杆菌病分子发病机制的认识,并为巴氏杆菌病的诊断标识筛选、新型疫苗创制和药物靶标筛选等提供基础数据。 相似文献
13.
Fatemeh Rafii Miseon Park Gonçalo Gamboa da Costa Luisa Camacho 《Archives of microbiology》2009,191(12):895-902
The production of short-chain fatty acids, reductive enzymes, and hydrolytic enzymes by four gatifloxacin-selected, fluoroquinolone-resistant,
mutant strains of C. perfringens, with stable mutations either in DNA gyrase or in both DNA gyrase and topoisomerase IV, was compared with that produced by
the wild-type parent strains to investigate the effect of mutations associated with the selection of gatifloxacin resistance
on bacterial metabolic activities. The mutants differed from their respective wild-type parent strains in the enzymatic activities
of azoreductase, nitroreductase, and β-glucosidase and in the ratio of butyric acid to acetic acid production. Microarray
analysis of one wild type and the corresponding mutant revealed different levels of mRNA expression for the enzymes involved
in short-chain fatty acid (SCFA) synthesis and for β-glucosidase and oxidoreductases. In addition to mutations in the target
genes, selection of resistance to gatifloxacin resulted in strain-specific physiological changes in the resistant mutants
of C. perfringens that affected their metabolic activities. 相似文献
14.
Christopher D. Gwenin Maher Kalaji Peter A. Williams Catherine M. Kay 《Biodegradation》2011,22(2):463-474
A kinetic comparison between three nitroreductase enzymes isolated from the genome of Bacillus licheniformis ATCC 14580 for prospective use as immobilised enzymes for explosives detection has been conducted. The genes encoding the
three enzymes (yfkO [BLNfnB] encoding an NfsB-like enzyme; nfrA [BLNfrA1] and ycnD [BLNfrA2] encoding PnrA-like enzymes) have been PCR amplified from the native genome and cloned into pET-28a(+) and a modified
cysteine(6)-tagged pET-28a(+) and subsequently over-expressed, purified, and biochemically characterised. The previously uncharacterised
nitroreductases exhibited activity against a wide range of explosives, including cyclic nitramines. Amino acid alignments
and overall structural comparisons with other nitroreductase family members suggest that the B. licheniformis enzymes are members of the NfsA-Frp/NfsB-FRase I family group. Despite the overall low amino acid identity, regions for flavin
mononucleotide binding and active site residues were highly conserved. 相似文献
15.
《Biocatalysis and Biotransformation》2013,31(3):222-226
AbstractN-Oxidation of arylamines to their corresponding nitrosobenzenes using a new chloroperoxidase purified from Musa paradisiaca stem juice has been examined. The enzymatic characteristics of the stem chloroperoxidase using 4-chloroaniline as substrate were determined. The Km values for 4-chloroaniline and H2O2 were 770 μM and 154 μM respectively, while the pH and temperature optima were 4.4 and 30°C respectively. The substrate specificities of the enzyme for the arylamines 3,4-dichloroamine, p-aminobenzoic acid, p-toluidine, p-anisidine, m-anisidine, p-aminophenol, o-aminophenol and m-aminophenol have been characterized. The feasibility of using concentrated M. paradisiaca stem juice for the specific conversion of 4-chloroaniline to 4-chloronitrosobenzene has been demonstrated. This enzyme can be used for the N-oxidation of other arylamines. 相似文献
16.
Andrew Willetts 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,632(3):454-463
Penicillium janthinellum is able to grow on glycine as the sole carbon and nitrogen source. The amino acid is transaminated to glyoxylate which is further metabolised to pyruvate by the glycerate pathway. The reaction product of partially purified glycerate kinase from this fungus is 2-phosphoglycerate. Phosphoglycerate mutase initiates gluconeogenesis from glycine. Partially purified phosphoglycerate mutase is inhibited by fructose 6-phosphate. The possible significance of this regulation is discussed. 相似文献
17.
Production and characterization of thermostable xylanase and pectinase from Streptomyces sp. QG-11-3
Q K Beg B Bhushan M Kapoor G S Hoondal 《Journal of industrial microbiology & biotechnology》2000,24(6):396-402
Streptomyces sp. QG-11-3, which produces a cellulase-free thermostable xylanase (96 IU ml−1) and a pectinase (46 IU ml−1), was isolated on Horikoshi medium supplemented with 1% w/v wheat bran. Carbon sources that favored xylanase production were
rice bran (82 IU ml−1) and birch-wood xylan (81 IU ml−1); pectinase production was also stimulated by pectin and cotton seed cake (34 IU ml−1 each). The partially purified xylanase and pectinase were optimally active at 60°C. Both enzymes were 100% stable at 50°C
for more than 24 h. The half-lives of xylanase and pectinase at 70, 75 and 80°C were 90, 75 and 9 min, and 90, 53 and 7 min,
respectively. The optimum pH values for xylanase and pectinase were 8.6 and 3.0, respectively, at 60°C. Xylanase and pectinase
were stable over a broad pH range between 5.4 and 9.4 and 2.0 to 9.0, respectively, retaining more than 85% of their activity.
Ca2+ stimulated the activity of both enzymes up to 7%, whereas Cd2+, Co2+, Cr3+, iodoacetic acid and iodoacetamide inhibited xylanase up to 35% and pectinase up to 63%; at 1 mM, Hg2+ inhibited both enzymes completely. Journal of Industrial Microbiology & Biotechnology (2000) 24, 396–402.
Received 29 September 1999/ Accepted in revised form 02 February 2000 相似文献
18.
Moonen MJ Rietjens IM van Berkel WJ 《Journal of industrial microbiology & biotechnology》2001,26(1-2):35-42
The biological Baeyer–Villiger oxidation of acetophenones was studied by 19F nuclear magnetic resonance (NMR). The 19F NMR method was used to characterise the time-dependent conversion of various fluorinated acetophenones in either whole cells
of Pseudomonas fluorescens ACB or in incubations with purified 4′-hydroxyacetophenone monooxygenase (HAPMO). Whole cells of P. fluorescens ACB converted 4′-fluoroacetophenone to 4-fluorophenol and 4′-fluoro-2′-hydroxyacetophenone to 4-fluorocatechol without the
accumulation of 4′-fluorophenyl acetates. In contrast to 4-fluorophenol, 4-fluorocatechol was further degraded as evidenced
by the formation of stoichiometric amounts of fluoride anion. Purified HAPMO catalysed the strictly NADPH-dependent conversion
of fluorinated acetophenones to fluorophenyl acetates. Incubations with HAPMO at pH 6 and 8 showed that the enzymatic Baeyer–Villiger
oxidation occurred faster at pH 8 but that the phenyl acetates produced were better stabilised at pH 6. Quantum mechanical
characteristics explained why 4′-fluoro-2′-hydroxyphenyl acetate was more sensitive to base-catalysed hydrolysis than 4′-fluorophenyl
acetate. All together, 19F NMR proved to be a valid method to evaluate the biological conversion of ring-substituted acetophenones to the corresponding
phenyl acetates, which can serve as valuable synthons for further production of industrially relevant chemicals. Journal of Industrial Microbiology & Biotechnology (2001) 26, 35–42.
Received 20 April 2000/ Accepted in revised form 16 September 2000 相似文献
19.
Antonio Rescigno Frédéric Bruyneel Alessandra Padiglia Francesca Sollai Andrea Salis Jaqueline Marchand-Brynaert Enrico Sanjust 《Biochimica et Biophysica Acta (BBA)/General Subjects》2011
Background
o-Aminophenols have been long recognised as tyrosinase substrates. However their exact mode of interaction with the enzyme's active site is unclear. Properly vic-substituted o-aminophenols could help gain some insight into tyrosinase catalytic mechanism.Methods
Eight vic-substituted o-aminophenols belonging to two isomeric series were systematically evaluated as tyrosinase substrates and/or activators and/or inhibitors, by means of spectrophotometric techniques and HPLC-MS analysis. Some relevant kinetic parameters have also been obtained.Results
Four o-aminophenolic compounds derived from 3-hydroxyorthanilic acid (2-amino-3-hydroxybenzenesulfonic acid) and their four counterparts derived from the isomeric 2-hydroxymetanilic acid (3-amino-2-hydroxybenzenesulfonic acid) were synthesised and tested as putative substrates for mushroom tyrosinase. While the hydroxyorthanilic derivatives were quite inactive as both substrates and inhibitors, the hydroxymetanilic compounds on the contrary all acted as substrates for the enzyme, which oxidised them to the corresponding phenoxazinone derivatives.General significance
Based on the available structures of the active sites of tyrosinases, the different affinities of the four metanilic derivatives for the enzyme, and their oxidation rates, we propose a new hypothesis regarding the interaction between o-aminophenols and the active site of tyrosinase that is in agreement with the obtained experimental results. 相似文献20.
Burkholderia sp. AA1 isolated from a diesel fuel-contaminated site degraded toluene, as well as a wide range of alkanes from decane (C8) to pentacosane (C25) as sole carbon and energy sources. This strain also utilized m-toluate, p-toluate, o-toluate, and m-cresol as sole carbon and energy sources. Toluene- and toluate-grown cells showed catechol 2,3-dioxygenase activity and indole
oxidation activity that is exhibited by some toluene oxygenation enzymes. The catechol 2,3-dioxygenase gene (catB) was cloned and sequenced. Its deduced amino acid sequence is analogous to the extradiol dioxygenases cloned from a variety
of microorganisms. A DNA fragment containing the genes for the indole oxidation activity was cloned and sequenced. A seven-gene
cluster designated as tbhABCDEFG was identified. Significant similarities were found with multicomponent monooxygenase systems for toluene, benzene and phenol
from different bacterial strains. Journal of Industrial Microbiology & Biotechnology (2000) 25, 127–131.
Received 28 July 1999/ Accepted in revised form 28 June 2000 相似文献