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1.
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
2.
Transformation of 2,4,6-trinitrotoluene (TNT) by <Emphasis Type="Italic">Raoultella</Emphasis> <Emphasis Type="Italic">terrigena</Emphasis> 总被引:1,自引:0,他引:1
Claus H Bausinger T Lehmler I Perret N Fels G Dehner U Preuss J König H 《Biodegradation》2007,18(1):27-35
Manufacture of nitroorganic explosives generates toxic wastes leading to contamination of soils and waters, especially groundwater.
For that reason bacteria living in environments highly contaminated with 2,4,6-trinitrotoluene (TNT) and other nitroorganic
compounds were investigated for their capacity for TNT degradation. One isolate, Raoultella terrigena strain HB, removed TNT at concentrations between 10 and 100 mg l−1 completely from culture supernatants under optimum aerobic conditions within several hours. Only low concentrations of nutrient
supplements were needed for the cometabolic transformation process. Radioactivity measurements with ring-labelled 14C–TNT detected about 10–20% of the initial radioactivity in the culture supernatant and the residual 80–90% as water-insoluble
organic compounds in the cellular pellet. HPLC analysis identified aminodinitrotoluenes (2-ADNT, 4-ADNT) and diaminonitrotoluenes
(2,4-DANT) as the metabolites which remained soluble in the culture medium and azoxy-dimers as the main products in the cell
extracts. Hence, the new isolate could be useful for the removal of TNT from contaminated waters. 相似文献
3.
A systematic evaluation of the ability of different bacterial genera to transform 2,4,6-trinitrotoluene (TNT), and grow in
its presence, was conducted. Aerobic Gram-negative organisms degraded TNT and evidenced net consumption of reduced metabolites
when cultured in molasses medium. Some Gram-negative isolates transformed all the initial TNT to undetectable metabolites,
with no adsorption of TNT or metabolites to cells. Growth and TNT transformation capacity of Gram-positive bacteria both exhibited
50% reductions in the presence of approximately 10 μg TNT ml−1. Most non-sporeforming Gram-positive organisms incubated in molasses media amended with 80 μg TNT ml−1 became unculturable, whereas all strains tested remained culturable when incubated in mineral media amended with 98 μg TNT
ml−1, indicating that TNT sensitivity is linked to metabolic activity. These results indicate that the microbial ecology of soil
may be severely impacted by TNT contamination.
Received: 2 December 1996 / Accepted: 3 February 1997 相似文献
4.
5.
Toluene dioxygenase (TDO) is ubiquitous in nature and has a broad substrate range, including benzene, toluene, ethylbenzene
and xylenes (BTEX). Pseudomonas putida F1 (PpF1) induced on toluene is known to produce indigo from indole through the activity of TDO. In this work, a spectrophotometric
assay previously developed to measure indole to indigo production rates was modified to characterize the effects of various
ethanol concentrations on toluene aerobic biodegradation activity and assess catabolite repression of TDO. Indigo production
rate by cells induced on toluene alone was 0.0012 ± 0.0006 OD610 min−1. The presence of ethanol did not fully repress TDO activity when toluene was also available as a carbon source. However,
indigo production rates by PpF1 grown on ethanol:toluene mixtures (3:1 w/w) decreased by approximately 50%. Overall, the proposed
spectrophotometric assay is a simple approach to quantify TDO activity, and demonstrates how the presence of ethanol in groundwater
contaminated with reformulated gasoline is likely to interfere with naturally occurring microorganisms from fully expressing
their aerobic catabolic potential towards hydrocarbons bioremediation. 相似文献
6.
Rohanah Hussain Christopher L. Joannou Giuliano Siligardi 《International journal of peptide research and therapeutics》2006,12(3):269-273
Microbes are increasingly developing defensive mechanisms against known drugs via mutations. There are signs of emergence of superbugs immune to most known antibiotics available. The need for a new class of drugs to counteract this problem is of paramount importance for continued general well being of mankind. A new class of drugs, antimicrobial peptides, has not been fully exploited primarily due to high cytotoxicity, poor lipophilicity preventing systemic distribution and stability. We have synthesised 9-amino acid residue cationic peptides RH01 and RH02 lipidated with myristoyl and octyl groups respectively. These peptides exhibited potent antimicrobial activity and low cytotoxicity. The lipopeptide RH01 has antimicrobial activity against a broad range of microorganisms including bacteria, yeast and filamentous fungi with greatest activity toward Gram-positive bacteria, including S. aureus MRSA stain, MIC’s ranging between 2–8 μM. The MIC for Gram-negative bacteria was higher ranging from between 30–250 μM. RH01 also had antimicrobial activity towards fungi showing good activity against the pathogenic yeast Candida albicans but was less active towards the filamentous fungi Aspergillus niger. The antimicrobial activity of RH01 as a measure of Ki(50) for E. coli and S. aureus was 35–60 μM and 3–7 μM, respectively. In-house data showed the compound is bactericidal even at higher bacteria concentration. The octylated lipopeptide RH02 has similar activities towards S. aureus (3.3 μM) and E coli (53.3 μM) as the myristolated RH01. There was no haemolytic activity of the lipopeptide RH01 towards human blood. Acute intravenous toxicity study in mice showed that both RH01 and RH02 induced no macroscopic abnormalities at their highest non-lethal dose of 75 mg/kg and 150 mg/kg bodyweight, respectively.Australian Peptide Conference Issue. 相似文献
7.
A. Eilers E. Rüngeling U. M. Stündl G. Gottschalk 《Applied microbiology and biotechnology》1999,53(1):75-80
Degradation of 2,4,6-trinitrotoluene (TNT) by the white-rot fungus Bjerkandera adusta DSM 3375 was studied in relation to extracellular ligninolytic activities. The Mn(II)-dependent peroxidase, the only ligninolytic
enzyme detectable, reached a maximum activity of 600 ± 159 U/l after incubation in mineral medium with a sufficient nitrogen
source. In contrast, the highest extent of [14C]TNT mineralization was detected in malt extract broth, so that the ability of B. adusta to mineralize TNT did not parallel ligninolytic activity. The microsomal fraction of cells grown in the presence of TNT was
found to contain 11 pmol cytochrome P-450/mg protein. In cells grown without TNT, no microsomal cytochrome P-450 could be found. Instead, 14 pmol P-450/mg protein was present in the cytosolic fraction of these cells. Cytochrome P-450 apparently affected the TNT metabolism, as shown by inhibitory studies. Addition of the cytochrome P-450 inhibitor piperonyl butoxide diminished the 14CO2 release from 21% to 0.9%, as determined after 23 days of incubation, while 1-aminobenzotriazole and metyrapone decreased
the mineralization to 8.6% and 6.3% respectively. Mass-balance analysis of TNT degradation in liquid cultures revealed that,
by inhibition of cytochrome P-450, the TNT-derived radioactivity associated with biomass and with polar, water-soluble metabolites decreased from 93.9%
to 15.0% and the fraction of radiolabelled metabolites extractable with organic solvents fell to 92.6%. The TNT metabolites
of this fraction were identified as aminodinitrotoluenes, indicating that this initial transformation product of TNT may function
as a substrate for cytochrome-P-450-dependent reactions in B. adusta.
Received: 27 May 1999 / Received revision: 19 August 1999 / Accepted: 19 August 1999 相似文献
8.
Mauricio Chávez-Avilés Alma Laura Díaz-Pérez Jesús Campos-García 《Molecular biology reports》2010,37(4):1787-1791
Pseudomonas aeruginosa is able to utilize leucine/isovalerate and acyclic terpenes as sole carbon sources. Key enzymes which play an important role
in these catabolic pathways are 3-hydroxy-3-methylglutaryl-coenzyme A (CoA) lyase (EC 4.1.3.4; HMG-CoA lyase) and the 3-hydroxy-3-isohexenylglutaryl-CoA
lyase (EC 4.1.2.26; HIHG-CoA lyase), respectively. HMG-CoA lyase is encoded by the liuE gene while the gene for HIHG-CoA lyase remains unidentified. A mutant in the liuE gene was unable to utilize both leucine/isovalerate and acyclic terpenes indicates an involvement of liuE in both catabolic pathways (Chávez-Avilés et al. 2009, FEMS Microbiol Lett 296:117–123). The LiuE protein was purified as
a His-tagged recombinant protein and in addition to show HMG-CoA lyase activity (Chávez-Avilés et al. 2009, FEMS Microbiol
Lett 296:117–123), also displays HIHG-CoA lyase activity, indicating a bifunctional role in both the leucine/isovalerate and
acyclic terpenes catabolic pathways. 相似文献
9.
B. G. Ferreira M. S. C. Freitas G. P. Bragana A. S. F. P. Moreira R. G. S. Carneiro R. M. S. Isaias 《Plant biology (Stuttgart, Germany)》2019,21(6):1052-1062
- The galls induced by Ditylenchus gallaeformans (Nematoda) on leaves of Miconia albicans have unique features when compared to other galls. The nematode colonies are surrounded by nutritive tissues with promeristematic cells, capable of originating new emergences facing the larval chamber, and providing indeterminate growth to these galls. Considering enzyme activity as essential for the translocation of energetic molecules from the common storage tissue (CST) to the typical nutritive tissue (TNT), and the major occurrence of carbohydrates in nematode galls, it was expected that hormones would mediate sink strength relationships by activating enzymes in indeterminate growth regions of the galls.
- Histochemical, immunocytochemical and quantitative analyses were made in order to demonstrate sites of enzyme activity and hormones, and comparative levels of total soluble sugars, water soluble polysaccharides and starch.
- The source–sink status, via carbohydrate metabolism, is controlled by the major accumulation of cytokinins in totipotent nutritive cells and new emergences. Thus, reducing sugars, such as glucose and fructose, accumulate in the TNT, where they supply the energy for successive cycles of cell division and for nematode feeding. The histochemical detection of phosphorylase and invertase activities indicates the occurrence of starch catabolism and sucrose transformation into reducing sugars, respectively, in the establishment of a gradient from the CST towards the TNT. Reducing sugars in the TNT are important for the production of new cell walls during the indeterminate growth of the galls, which have increased levels of water‐soluble polysaccharides that corroborate such a hypothesis.
- Functional relationship between plant hormone accumulation, carbohydrate metabolism and cell differentiation in D. gallaeformans‐induced galls is attested, providing new insights on cell development and plant metabolism.
10.
The major enzyme in Clostridium acetobutylicum ATCC 824 leading to transformation of TNT has been reported to be the Fe-only hydrogenase. In this study, we examine the effect of inhibitors of hydrogenase on TNT reduction by Clostridial extracts. These experiments further demonstrate the major role of hydrogenase in TNT transformation. The C. acetobutylicum hydrogenase is closely related to that of C. pasteurianum; and can be fitted to the X-ray crystal structure with a root mean square deviation of 1.18 Å for the Cα atoms of the generated 3D simulation model. The Hyd1, Hyd2, and Hyd3 antibodies generated against hydrogenase reacted with both the hydrogenase in cell extracts and with C. acetobutylicum hydrogenase expressed in Escherichia coli. Inhibition studies using antibodies against Fe-only hydrogenase from C. acetobutylicum indicated that the transformation of TNT by crude cell extracts was completely inhibited by Hyd2 antibody (to amino acid 415–428) whereas antibodies Hyd1 (to residues 1–16) and Hyd3 (to amino acid 424–448) inhibited less effectively. The TNT transforming activity of the cell extract was retained when Hyd2 antibody pretreated with purified but enzymatically inactive recombinant hydrogenase was added to the extract. Addition of the transition metal Cu (2+) to extracts completely inhibited the transformation of TNT suggesting the destruction of [4Fe–4S] centers which are essential for transfer of electrons from the H2-activating site to TNT. Growth of C. acetobutylicum was also inhibited by 0.5 mM Cu(2+) and Hg(2+) ions. The triazine dye, procion red and the nitroimidazole drug, metronidazole inhibit TNT reduction. The inhibition studies using antibodies, procion red, metronidazole, and transition metals suggest that different portions of hydrogenase are required for effective TNT reduction. 相似文献
11.
Noomen Hmidet Nedra El Hadj Ali Nahed Zouari-Fakhfakh Anissa Haddar Moncef Nasri Alya Sellemi-Kamoun 《Journal of industrial microbiology & biotechnology》2010,37(9):983-990
This study is concerned with the co-production of alkaline proteases and thermostable α-amylase by some feather-degrading
Bacillus strains: B. mojavensis A21, B. licheniformis NH1, B. subtilis A26, B. amyloliquefaciens An6 and B. pumilus A1. All strains produced both enzymes, except B. pumilus A1, which did not exhibit amylolytic activity. The best enzyme co-production was obtained by the NH1 strain when chicken
feathers were used as nitrogen and carbon sources in the fermentation medium. The higher co-production of both enzymes by
B. licheniformis NH1 strain was achieved in the presence of 7.5 g/l chicken feathers and 1 g/l yeast extract. Strong catabolic repression
on protease and α-amylase production was observed with glucose. Addition of 0.5% glucose to the feather medium suppressed
enzyme production by B. licheniformis NH1. The growth of B. licheniformis NH1 using chicken feathers as nitrogen and carbon sources resulted in its complete degradation after 24 h of incubation at
37°C. However, maximum protease and amylase activities were attained after 30 h and 48 h, respectively. Proteolytic activity
profiles of NH1 enzymatic preparation grown on chicken feather or casein-based medium are different. As far as we know, this
is the first contribution towards the co-production of α-amylase and proteases using keratinous waste. Strain NH1 shows potential
use for biotechnological processes involving keratin hydrolysis and industrial α-amylase and proteases co-production. Thus,
the utilization of chicken feathers may result in a cost-effective process suitable for large-scale production. 相似文献
12.
Twenty-one ruminal bacteria species were tested for their ability to degrade 2,4,6-trinitrotoluene (TNT) within 24 h. Butyrivibrio fibrisolvens, Fibrobacter succinogenes, Lactobacillus vitulinus, Selenomonas ruminantium, Streptococcus caprinus, and Succinivibrio dextrinosolvens were able to completely degrade 100 mg/L TNT, with <5% of the original TNT recovered as diaminonitrotoluene metabolites.
Eubacterium ruminantium, Lactobacillus ruminis, Ruminobacter amylophilus, Streptococcus bovis, and Wolinella succinogenes were able to completely degrade 100 mg/L TNT, with 23–60% of the TNT recovered as aminodinitrotoluene and/or diaminonitrotoluene
metabolites. Clostridium polysaccharolyticum, Megasphaera elsdenii, Prevotella bryantii, Prevotella ruminicola, Ruminococcus albus, and Ruminococcus flavefaciens were able to degrade 80–90% of 100 mg/L TNT. Desulfovibrio desulfuricans subsp. desulfuricans, Prevotella albensis, and Treponema bryantii degraded 50–80% of the TNT. Anaerovibrio lipolytica was completely inhibited by 100 mg/L TNT. These results indicate that a variety of rumen bacteria is capable of transforming
TNT. 相似文献
13.
The assessment of biodegradation activity in contaminated aquifers is critical to demonstrate the performance of bioremediation
and natural attenuation and to parameterize models of contaminant plume dynamics. Real time quantitative PCR (qPCR) was used
to target the catabolic bssA gene (coding for benzylsuccinate synthase) and a 16S rDNA phylogenetic gene (for total Bacteria) as potential biomarkers to infer on anaerobic toluene degradation rates. A significant correlation (P = 0.0003) was found over a wide range of initial toluene concentrations (1–100 mg/l) between toluene degradation rates and
bssA concentrations in anaerobic microcosms prepared with aquifer material from a hydrocarbon contaminated site. In contrast,
the correlation between toluene degradation activity and total Bacteria concentrations was not significant (P = 0.1125). This suggests that qPCR targeting of functional genes might offer a simple approach to estimate in situ biodegradation
activity, which would enhance site investigation and modeling of natural attenuation at hydrocarbon-contaminated sites. 相似文献
14.
Smita Dube Kamna Nanda Reema Rani Namrata Jit Kaur Jatin Kumar Nagpal Dilip J. Upadhyay Ian A. Cliffe Kulvinder Singh Saini Kedar P. Purnapatre 《World journal of microbiology & biotechnology》2010,26(9):1623-1629
Multi-drug resistant Pseudomonas aeruginosa (MDRPA) are emerging as a major threat in the hospitals as they have become resistant to current antibiotics. There is an
immediate requirement of drugs with novel mechanisms as the pipeline of investigational drugs against these organisms is lean.
UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) enzyme that catalyzes the first committed step of bacterial cell wall
biosynthesis is an ideal target for the discovery of novel antibiotics against Gram negative pathogens as they have only one
copy of murA gene in its genome. We have performed biochemical characterization and comparative kinetic analysis of MurA from E. coli and P. aeruginosa. Both enzymes were active at broad range of pH with temperature optima of 37°C. Metal ions did not enhance the activity of
both enzymes. These enzymes had an apparent affinity constant (K
m
) for its substrate UDP-N-acetylglucosamine 36 ± 5.2 and 17.8 ± 2.5 μM and for phosphoenolpyruvate 0.84 ± 0.13 μM and 0.45 ± 0.07 μM
for E. coli and P. aeruginosa enzymes respectively. Both the enzymes showed 5–7 fold shift in IC50 for the known inhibitor fosfomycin upon pre-incubation with the substrate UDP-N-acetylglucosamine. This observation was used
to develop a novel rapid sensitive high throughput assay for the screening of MurA inhibitors. 相似文献
15.
The synthesis of carotenoids begins with the formation of a phytoene from geranylgeranyl pyrophosphate, a well conserved
step in all carotenogenic organisms and catalyzed by a phytoene synthase, an enzyme encoded by the crtB (spy) genes. The next step is the dehydrogenation of the phytoene, which is carried out by phytoene dehydrogenase. In organisms
with oxygenic photosynthesis, this enzyme, which accomplishes two dehydrogenations, is encoded by the crtP genes. In organisms that lack oxygenic photosynthesis, dehydrogenation is carried out by an enzyme completely unrelated to
the former one, which carries out four dehydrogenations and is encoded by the crtI genes. In organisms with oxygenic photosynthesis, dehydrogenation of the phytoene is accomplished by a ζ-carotene dehydrogenase
encoded by the crtQ (zds) genes. In many carotenogenic organisms, the process is completed with the cyclization of lycopene. In organisms exhibiting
oxygenic photosynthesis, this step is performed by a lycopene cyclase encoded by the crtL genes. In contrast, anoxygenic photosynthetic and non-photosynthetic organisms use a different lycopene cyclase, encoded
by the crtY (lyc) genes. A third and unrelated type of lycopene β-cyclase has been described in certain bacteria and archaea. Fungi differ
from the rest of non-photosynthetic organisms in that they have a bifunctional enzyme that displays both phytoene synthase
and lycopene cyclase activity. Carotenoids can be modified by oxygen-containing functional groups, thus originating xanthophylls.
Only two enzymes are necessary for the conversion of β-carotene into astaxanthin, using several ketocarotenoids as intermediates,
in both prokaryotes and eukaryotes. These enzymes are a β-carotene hydroxylase (crtZ genes) and a β-carotene ketolase, encoded by the crtW (bacteria) or bkt (algae) genes.
Electronic Publication 相似文献
16.
Klebsiella sp. strain C1 isolated from activated sludge metabolized 2,4,6-trinitrotoluene (TNT) by two different pathways. The typical metabolites in the nitro group reduction pathway of TNT, such as hydroxylamino-dinitrotoluenes and amino-dinitrotoluenes, were detected. Dinitrotoluenes and nitrite were also detected, possibly produced by a denitration pathway. After incubation of [U-14C]TNT for 28 and 77 d, 2.4 and 6.24%, respectively, were released as 14CO2. This mineralization rate was higher than those reported by any other TNT degrading bacteria and might be due to the dual pathways of degradation in this bacterium. 相似文献
17.
Tanner JJ 《Amino acids》2008,35(4):719-730
The proline catabolic enzymes proline dehydrogenase and Δ1-pyrroline-5-carboxylate dehydrogenase catalyze the 4-electron oxidation of proline to glutamate. These enzymes play important
roles in cellular redox control, superoxide generation, apoptosis and cancer. In some bacteria, the two enzymes are fused
into the bifunctional enzyme, proline utilization A. Here we review the three-dimensional structural information that is currently
available for proline catabolic enzymes. Crystal structures have been determined for bacterial monofunctional proline dehydrogenase
and Δ1-pyrroline-5-carboxylate dehydrogenase, as well as the proline dehydrogenase and DNA-binding domains of proline utilization
A. Some of the functional insights provided by analyses of these structures are discussed, including substrate recognition,
catalytic mechanism, biochemical basis of inherited proline catabolic disorders and DNA recognition by proline utilization
A. 相似文献
18.
Wojcieszyńska D Guzik U Greń I Perkosz M Hupert-Kocurek K 《World journal of microbiology & biotechnology》2011,27(4):805-811
Stenotrophomonas maltophilia KB2 is known to produce different enzymes of dioxygenase family. The aim of our studies was to determine activity of these
enzymes after induction by benzoic acids in cometabolic systems with nitrophenols. We have shown that under cometabolic conditions
KB2 strain degraded 0.25–0.4 mM of nitrophenols after 14 days of incubation. Simultaneously degradation of 3 mM of growth
substrate during 1–3 days was observed depending on substrate as well as cometabolite used. From cometabolic systems with
nitrophenols as cometabolites and 3,4-dihydroxybenzoate as a growth substrate, dioxygenases with the highest activity of protocatechuate
3,4-dioxygenase were isolated. Activity of catechol 1,2- dioxygenase and protocatechuate 4,5-dioxygenase was not observed.
Catechol 2,3-dioxygenase was active only in cultures with 4-nitrophenol. Ability of KB2 strain to induce and synthesize various
dioxygenases depending on substrate present in medium makes this strain useful in bioremediation of sites contaminated with
different aromatic compounds. 相似文献
19.
Glutamate dehydrogenase of the germinating triticale seeds: gene expression,activity distribution and kinetic characteristics 总被引:1,自引:0,他引:1
On the cross-roads of main carbon and nitrogen metabolic pathways, glutamate dehydrogenase (GDH, E.C. 1.4.1.2) carries out
the reaction of reductive amination of 2-oxoglutarate to glutamate (the anabolic activity; NAD(P)H–GDH), and the reverse reaction
of oxidative deamination of glutamic acid (the catabolic activity; NAD(P)+–GDH). To date, there have been no reports on identification of GDH genes in cereals. Here, we report cloning and biochemical characterization of the GDH from germinating triticale seeds, a
common Polish cereal. A single TsGDH1 gene is 1,620 bp long, while its 1,236 bp long open reading frame encodes a protein of 411 amino acids of high homology with
the published GDH protein sequences from other plants. Phylogenetic analyses locate the TsGDH1 among other monocotyledonous
proteins and among the sequences of the β-type subunit of plant GDHs. Changes in TsGDH1 expression and the dynamics of enzyme activity in germinating seeds confirm the existence of one TsGDH isoform with varying
expression and activity patterns, depending on the tissue localization and stage of germination. The four-step purification
method (including the anionite chromatography using HPLC) resulted in a protein preparation with a high-specific activity
and purification factor of approx. 230. The purified enzyme exhibited an absolute specificity towards 2-oxoglutarate (NAD(P)H–GDH),
or towards l-glutamate in the reverse reaction (NAD(P)+–GDH), while its low K
m constants towards all substrates and co-enzymes may suggest its aminating activity during germination, or, alternatively,
its capability to adjust the direction of the catalyzed reaction according to the metabolic necessity. 相似文献
20.
P. L. Schuerman J. S. Liu H. Mou A. M. Dandekar 《Applied microbiology and biotechnology》1997,47(5):560-565
Escherichia coli strains that did not have the ability to use sucrose as a sole carbon source gained this ability after receiving a cloned
fragment of DNA from Agrobacterium tumefaciens. No invertase was detected in the sucrose-metabolizing E. coli, but evidence for the activity of certain enzymes, known to be produced by biotype 1 strains of Agrobacterium, were found. Evidence was found for the presence of d-glucoside 3-dehydrogenase (G3DH) and α-3-ketoglucosidase. The activity of enzyme extracts on 3-ketosucrose also indicated
that 3-ketoglucose reductase, or some enzyme that acts on 3-ketoglucose, was present in the Suc+
E. coli as well. The fragment was found to complement a G3DH mutant of A. tumefaciens and was also found to confer chemotaxis towards sucrose in E. coli.
Received: 13 September 1996 / Received revision: 15 January 1997 / Accepted: 24 January 1997 相似文献