共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Garforth J. H. McKie R. Jaouhari T. J. Benson A. H. Fairlamb K. T. Douglas 《Amino acids》1994,6(3):295-299
Summary The rational design of ligands for the substrate-binding site of a homology-modelled trypanothione reductase (TR) was performed. Peptides were designed to be selective for TR over human glutathione reductase (GR). The design process capitalized on the proposed differences between the activesites of TR and human GR, subsequently confirmed by the TR crystal structure. Enzyme kinetics confirmed that forT. cruzi TR benzoyl-Leu-Arg-Arg-ß-naphthylamide was an inhibitor (Ki 13.8µM) linearly competitive with the native substrate, trypanothione disulphide, and did not inhibit glutathione reductase. 相似文献
2.
Summary. Trypanosomatids depend on spermidine for growth and survival. Consequently, enzymes involved in spermidine synthesis and utilization,
i.e. arginase, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC), spermidine synthase, trypanothione synthetase (TryS), and trypanothione reductase
(TryR), are promising targets for drug development. The ODC inhibitor α-difluoromethylornithine (DFMO) is about to become
a first-line drug against human late-stage gambiense sleeping sickness. Another ODC inhibitor, 3-aminooxy-1-aminopropane (APA),
is considerably more effective than DFMO against Leishmania promastigotes and amastigotes multiplying in macrophages. AdoMetDC inhibitors can cure animals infected with isolates from
patients with rhodesiense sleeping sickness and leishmaniasis, but have not been tested on humans. The antiparasitic effects
of inhibitors of polyamine and trypanothione formation, reviewed here, emphasize the relevance of these enzymes as drug targets.
By taking advantage of the differences in enzyme structure between parasite and host, it should be possible to design new
drugs that can selectively kill the parasites. 相似文献
3.
Luiz H. Rosa Betania B. Cota Kátia M. G. Machado Carlos A. Rosa Carlos L. Zani 《World journal of microbiology & biotechnology》2005,21(6-7):983-987
Summary The ethyl acetate extract from the fungus Oudemansiella canarii grown in malt extract medium was evaluated against (a) the recombinant enzyme trypanothione reductase from Trypanosoma cruzi, (b) lymphocyte proliferation in human peripheral blood mononuclear cells (PBMCs) stimulated with phytohaemaglutinin, (c)
the human tumour cell lineages MCF-7, TK-10 and UACC-62, and (d) the phytopathogenic fungus Cladosporium sphaerospermum. At 10 μg/ml, the crude extract was inactive against PBMC but inhibited the growth of UACC-62 cells by 47% and the enzyme
trypanothione reductase (TryR). It also presented strong inhibition in the bioautographic assay with C. sphaerospermum. Chromatographic fractionation guided by this assay allowed the isolation of oudemansin A (1), a known fungitoxic compound
that showed a minimum inhibitory concentration (MIC) of 1.25 μg/spot in the bioautographic assay. As oudemansin A was not
active in the other assays, other components in the extract may be responsible for the observed activities by the crude extract
against the UACC-62 cells or the TryR enzyme. 相似文献
4.
Irena Romanowska Ewa Kwapisz Magdalena Mitka Stanisław Bielecki 《Journal of industrial microbiology & biotechnology》2010,37(6):625-629
Gordonia alkanivorans S7 is an efficient degrader of fuel oil hydrocarbons that can simultaneously utilize oxygen and nitrate as electron acceptors.
The respiratory nitrate reductase (Nar) from this organism has been isolated using ion exchange chromatography and gel filtration,
and then preliminarily characterized. PAGE, SDS-PAGE and gel filtration chromatography revealed that Nar consisted of three
subunits of 103, 53 and 25 kDa. The enzyme was optimally active at pH 7.9 and 40°C. K
m values for NO3
− (110 μM) and for ClO3
− (138 μM) were determined for a reduced viologen as an electron donor. The purified Nar did not use NADH as the electron donor
to reduce nitrate or chlorate. Azide was a strong inhibitor of its activity. Our results imply that enzyme isolated from G. alkanivorans S7 is a respiratory membrane-bound nitrate reductase. This is the first report of purification of a nitrate reductase from
Gordonia species. 相似文献
5.
Spinach (Spinacea oleracea L.) nitrate reductase (NR) is inactivated by phosphorylation on serine-543, followed by binding of the phosphorylated enzyme
to 14-3-3 proteins. We purified one of several chromatographically distinct NRserine-543 kinases from spinach leaf extracts, and established by Edman sequencing of 80 amino acid residues that it is a calcium-dependent
(calmodulin-domain) protein kinase (CDPK), with peptide sequences very similar to Arabidopsis CDPK6 (accession no. U20623; also known as CPK3). The spinach CDPK was recognized by antibodies raised against Arabidopsis CDPK. Nitrate reductase was phosphorylated at serine-543 by bacterially expressed His-tagged CDPK6, and the phosphorylated
NR was inhibited by 14-3-3 proteins. However, the bacterially expressed CDPK6 had a specific activity approx. 200-fold lower
than that of the purified spinach enzyme. The physiological control of NR by CDPK is discussed, and the regulatory properties
of the purified CDPK are considered with reference to current models for reversible intramolecular binding of the calmodulin-like
domain to the autoinhibitory junction of CDPKs.
Received: 12 February 1998 / Accepted: 28 May 1998 相似文献
6.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):161-173
AbstractTrypanothione reductase, the enzyme which in trypanosomal and leishmanial parasites catalyses the reduction of trypanothione disulphide to the redox-protective dithiol and has been identified as a potential target for rational antiparasite drug design, has been found to be strongly inhibited by tricyclic compounds containing the saturated dibenzazepine (imipramine) nucleus, with Ki values in the low micromolar range. This drug lead structure was designed by molecular graphics analysis of a three-dimensional homology model, focussing on the active-site. Inhibition studies were carried out to determine the effect of inhibitor structure on the inhibitory strength towards recombinant trypanothione reductase from Trypanosoma cruzi Hansch analysis showed that inhibitory strength depended on terms in 2 and s`m indicating dependence on both lipophilicity and inductive effect for ring-substituted analogues of imipramine. The side-chain ω-aminoalkyl chain had to be longer than 2-carbon units for inhibition. The effect on inhibition strength of the substituent at the ω-amino position on the side-chain of the central ring nitrogen atom depended markedly on the detailed substitution pattern of the rest of the molecule. This provides kinetic evidence studies of multiple binding modes within a single, blanket binding site for the inhibitor with the tricyclic ring system in the general region of the hydrophobic pocket lined by Trp21, Tyr110, Met113 and Phe114. This aspect of the structural sensitivity of the precise active-site triangulation adopted by the inhibitor is probably a function of the use of hydrophobic interactions of low directional specificity in this pocket combined with an electrostatianchoring by the ω-N+HMe2 function of the inhibitor, presumably with a glutamate sidethain, such as Glu-18, Glu-466prime; and/or Glu-467prime;. 相似文献
7.
Trypanothione reductase from Trypanosoma cruzi. Catalytic properties of the enzyme and inhibition studies with trypanocidal compounds 总被引:3,自引:0,他引:3
M C Jockers-Scherübl R H Schirmer R L Krauth-Siegel 《European journal of biochemistry》1989,180(2):267-272
Trypanothione reductase of Trypanosoma cruzi is a key enzyme in the antioxidant metabolism of the parasite. Here we report on the enzymic and pharmacological properties of trypanothione reductase using glutathionylspermidine disulfide as a substrate. 1. Both pH optimum (7.5) and the ionic strength optimum (at 30 mM) are unusually narrow for this enzyme. 40 mM Hepes, 1 mM EDTA, pH 7.5 was chosen as a standard assay buffer because in this system the kcat/Km ratio had the highest values for both natural substrates, glutathionylspermidine disulfide (2.65 x 10(6) M-1 s-1) and trypanothione disulfide (4.63 x 10(6) M-1 s-1). 2. Using the standardized assay, trypanothione reductase and the phylogenetically related host enzyme, human glutathione reductase, were studied as targets of inhibitors. Both enzymes, in their NADPH-reduced forms, were irreversibly modified by the cytostatic agent, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Nifurtimox, the drug used in the treatment of Chagas' disease, is a stronger inhibitor of glutathione reductase (Ki = 40 microM) than of trypanothione reductase (IC50 = 200 microM). 3. Of the newly synthesized trypanocidal compounds [Henderson, G. B., Ulrich, P., Fairlamb, A. H., Rosenberg, I., Pereira, M., Sela, M. & Cerami, A. (1988) Proc. Natl Acad. Sci., 85, 5374-5378] a nitrofuran derivative, 2-(5-nitro-2-furanylmethylidene)-N,N'-[1,4-piperazinediylbis (1,3-propanediyl)]bishydrazinecarboximidamide tetrahydrobromide, was found to be a better inhibitor for trypanothione reductase (Ki = 0.5 microM) than for glutathione reductase (IC50 = 10 microM). A naphthoquinone derivative, 2,3-bis[3-(2-amidinohydrazono)-butyl]-1,4-naphthoquinone dihydrochloride, turned out to be both an inhibitor (IC50 = 1 microM) and an NADPH-oxidation-inducing substrate (Km = 14 microM). This effect was not observed with human glutathione reductase. Such compounds which lead to oxidative stress by more than one mechanism in the parasite are promising starting points for drug design based on the three-dimensional structures of glutathione and trypanothione reductases. 相似文献
8.
Cell-free extracts (CFEs) of chromium-resistant bacterium Bacillus sphaericus AND 303 isolated from serpentine soil of Andaman, India reduced Cr(VI) in in vitro condition, and the reductase activity was solely localized in the soluble cell-fractions (S12, S32, and S150). The enzyme was constitutive as the CFEs from cells grown in Cr(VI)-free and Cr(VI)-containing media reduced a more or less
equal amount of Cr(VI). Optimum Cr(VI) reductase activity was obtained at an enzyme (S150) concentration equivalent to 4.56 mg protein/mL, 300 μM Cr(VI) and pH 6.0 after 30 min incubation at 30°C. The enzyme was heat labile; 80% of its activity was lost when exposed
at 70°C for 15 min. Kinetics of Cr(VI) reductase activity fit well with the linearized Lineweaver-Burk plot and showed a Vmax of 1.432 μmol Cr(VI)/mg protein/min and Km of 158.12 μM Cr(VI). The presence of additional electron donors accelerated Cr(VI) reductase activity of CFE, and an increase of 28% activity
over control was recorded with 1.0 μM NADH. Heavy metal ions such as Ni(II), Cu(II), and Cd(II) were strong inhibitors of Cr(VI) reductase unlike that of 100 μM Co(II), which retained 93% activity over control. 相似文献
9.
P. V. Ershov O. V. Gnedenko A. A. Molnar A. V. Lisitsa A. S. Ivanov A. I. Archakov 《Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry》2012,6(1):94-97
The analysis of kinetic and thermodynamic parameters of binding of peptide and nonpeptide dimerization inhibitors of HIV protease
(HIVp) to the enzyme monomers immobilized on an optical chip has been studied by surface plasmon resonance. The molecular
interactions were investigated at different inhibitor concentrations (0–80 μM) and temperatures (15–35°C). Determination of
kinetic (k
on, k
off), equilibrium (K
d), and thermodynamic (ΔG, ΔH, and -TΔS) has shown that both inhibitors are characterized by similar interaction parameters and the entropic term (-TΔS) of about −20 kcal/mol is the main driving force for the HIVp complex formation with the inhibitors, while the positive value
(14 kcal/mol) of the enthalpic term (ΔH) counteracted the complex formation. 相似文献
10.
Several pentavalent antimony compounds have been used for the treatment of leishmaniasis for decades. However, the mechanism of these antimony drugs still remains unclear. One of their targets is thought to be trypanothione, a major low molecular mass thiol inside the parasite. We show that pentavalent antimony (SbV) can be rapidly reduced to its trivalent state by trypanothione at mildly acidic conditions and 310 K (k=4.42 M–1 min–1 at pH 6.4), and that SbIII can be bound to trypanothione to form an SbIII-trypanothione complex. NMR data demonstrate that SbIII binds to trypanothione at the two thiolates of the cysteine residues, and that the binding is pH dependent and is strongest at biological pH with a stability constant logK=23.6 at 298 K (0.1 M NaNO3). The addition of low molecular monothiol ligands such as glutathione and cysteine to the SbIII-trypanothione complex results in the formation of a ternary complex. Thiolates from both trypanothione and monothiol bind to the SbIII center. The formation of the ternary complex is important, as the antileishmanial properties of the drugs are probably due to a complex between of SbIII-trypanothione and enzymes. Although thermodynamically stable, the complex is kinetically labile and the free and bound forms of thiolates exchange on the 1H NMR timescale. Such a facile exchange may be crucial for the transport of SbIII within parasites.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.Abbreviations amastigote the parasites culture at pH 5.0 and 310 K to resume the intracellular form - BPR bromopyrogallol - ESI-MS electrospary ionization mass spectrometry - GSH glutathione - pH* pH meter reading in D2O without correction for isotope effects - promastigote the parasites culture at pH 7.4 and 298 K to resume the extracellular stage - T(SH)2 reduced form of trypanothione - T(S-S) oxidized form of trypanothione (disulfide form) - TR trypanothione reductase - tart tartrate 相似文献
11.
Aftab Alam 《Journal of biosciences》1986,10(1):37-47
Dihydrofolate reductase has been purified from a methotrexate-resistant human lymphoid cell line (CCRF/CEM-R3) and up to 1
mg of enzyme has been obtained from 5 litres of culture. The enzyme has a molecular weight of 22000 ±500 as determined by
gel filtration. The pH activity profile shows a single optimum at pH 7.7, where marked activation is observed by addition
of 0.2 M NaCl. TheK
m for NADPH is 3μM and dihydrofolate 0.7μM. The binding constant for the inhibitor, methotrexate, is 29 pM 相似文献
12.
Luiz H. Rosa Elaine M. Souza-Fagundes Kátia M.G. Machado Tânia M. A. Alves Olindo A. Martins-Filho Alvaro J. Romanha Rodrigo C. Oliveira Carlos A. Rosa Carlos L. Zani 《World journal of microbiology & biotechnology》2006,22(6):539-545
Summary The ethyl acetate extract from the culture of the fungus Agrocybe perfecta (Rick) Singer was selected for further study in a screening of Brazilian basidiomycetes for bioactivity. The extract showed
significant activity against the recombinant enzyme trypanothione reductase (TryR) from Trypanosoma cruzi, lymphocyte proliferation in human peripheral mononuclear cells (PBMC) stimulated with phytohemaglutinin (PHA), and the human
cancer cell lines UACC-62 (melanoma), MCF-7 (mammary), and TK-10 (kidney). The chromatographic fractionation of the extract
was monitored by the above bioassays and showed that agrocybin was the active component. Agrocybin, a known polyacetylene
amide, showed an IC50 of 2 μM in the TryR assay but killed only 60% of the trypomastigote form of T. cruzi in infected murine blood even at 680 μM. This weaker activity could be due to the low temperature used to mimic banked blood
or as a consequence of its inactivation by blood, already reported in the literature. On the other hand, it inhibited the
proliferation of PBMC by 50% at 3.4 μM and the growth of the cancer cell lines at concentrations between 9 and 24.5 μM. Measurements
of DNA fragmentation using flow cytometry suggest that agrocybin promotes cell death via apoptosis. 相似文献
13.
Mineralisation of 14C-labelled synthetic lignin and ligninolytic enzyme activities of litter-decomposing basidiomycetous fungi 总被引:4,自引:0,他引:4
Within a screening program, 27 soil litter-decomposing basidiomycetes were tested for ligninolytic enzyme activities using
agar-media containing 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonate), a humic acid or Mn2+ ions as indicator substrates. Most active species were found within the family Strophariaceae (Agrocybe praecox, Stropharia coronilla, S. rugosoannulata) and used for mineralisation experiments with a 14C-ring-labelled synthetic lignin (14C-DHP). The fungi mineralised around 25% of the lignin to 14CO2 within 12 weeks of incubation in a straw environment; about 20% of the lignin was converted to water-soluble fragments. Mn-peroxidase
was found to be the predominant ligninolytic enzyme of all three fungi in liquid culture and its production was strongly enhanced
in the presence of Mn2+ ions. The results of this study demonstrate that certain ubiquitous litter-decomposing basidiomycetes possess ligninolytic
activities similar to the wood-decaying white-rot fungi, the most efficient lignin degraders in nature.
Received: 20 April 2000 / Received revision: 12 July 2000 / Accepted: 16 July 2000 相似文献
14.
Expression of Trypanosoma congolense trypanothione reductase in Escherichia coli: overproduction, purification, and characterization 总被引:2,自引:0,他引:2
The cloned trypanothione reductase gene from Trypanosoma congolense has been expressed in Escherichia coli to a level of 1% of the soluble protein. This has allowed facile purification and initial characterization of the reductase, and it appears by all criteria to be a representative member of the trypanothione reductase family. Most importantly, it shows the same exclusive substrate specificity for trypanothione over glutathione characteristic of other trypanothione reductases examined to date. The availability of the pure, cloned, sequenced reductase from T. congolense makes this enzyme a good target for structure/function studies and trypanocidal inhibitor design. 相似文献
15.
Whole cultures of Nocardia sp. NRRL 5646 reduce carboxylic acids, first to aldehydes, then to alcohols and subsequently to the corresponding acetyl
esters. This work describes an NADPH-dependent reductase responsible for catalyzing the reduction of aldehyde intermediates,
which was purified 3240-fold by a combination of Mono-Q, hydroxyapatite, and ADP-agarose chromatographies. By sodium dodecyl
sulfate–polyacrylamide gel electrophoresis, the purified enzyme ran as a single band of 47 kDa. A native molecular mass estimated
at 101 kDa indicated that the enzyme was a homodimer in the native, active state. Edman degradation indicated a unique N-terminal
sequence as NH2-X-X-Ala-Ala-Ala-Tyr-Ala-Val-Pro-Ala-Pro-Asp-Gly-Cys-Phe-Glu-Lys-Val-Thr-Ile-Glu-Arg-Arg-Glu-Leu-Gly. The enzyme catalyzed
reductions of many aryl- and alkyl-aldehyde substrates. Reactions were most favorable in the direction of aldehyde reduction
to alcohols. Journal of Industrial Microbiology & Biotechnology (2000) 25, 328–332.
Received 08 May 2000/ Accepted in revised form 20 October 2000 相似文献
16.
Martinus A.M. van Boekel Daan M.F. van Aalten Gert-Jan Caspers Beate Röll Wilfried W. de Jong 《Journal of molecular evolution》2001,52(3):239-248
ρB-crystallin (AJ245805) is a major protein component (20%) in the eye lens of the gecko Lepidodactylus lugubris. Limited peptide sequence analysis earlier revealed that it belongs to the aldo-keto reductase superfamily, as does the frog
lens ρ-crystallin. We have now determined the complete cDNA sequence of ρB-crystallin and established that it is more closely
related to the aldose reductase branch of the superfamily than to frog ρ-crystallin. These gecko and frog lens proteins have
thus independently been recruited from the same enzyme superfamily. Aldose reductase is implicated in the development of diabetic
cataract in mammals, and, if active, ρB-crystallin might be a potential risk for the gecko lens. Apart from a replacement
298 Cys → Tyr, ρB-crystallin possesses all amino acid residues thought to be required for catalytic activity of the aldose
reductases. However, modeling studies of the ρB-crystallin structure indicate that substrate specificity and nicotinamide
cofactor affinity might be affected. Indeed, neither recombinant ρB-crystallin nor the reverse mutant 298 Tyr → Cys showed
noticeable activity toward aliphatic and aromatic substrates, although cofactor binding was retained. Various other oxidoreductases
are known to be recruited as abundant lens proteins in many vertebrate species; ρB-crystallin demonstrates that an aldose
reductase-related enzyme also can be modified to this end.
Received: 18 July 2000 / Accepted: 3 November 2000 相似文献
17.
Hoyt MA Williams-Abbott LJ Pitkin JW Davis RH 《Molecular & general genetics : MGG》2000,263(4):664-673
S-adenosylmethionine decarboxylase (AdoMetDC) catalyzes the formation of decarboxylated AdoMetDC, a precursor of the polyamines
spermidine and spermine. The enzyme is derived from a proenzyme by autocatalytic cleavage. We report the cloning and regulation
of the gene for AdoMetDC in Neurospora crassa, spe-2, and the effect of putrescine on enzyme maturation and activity. The gene was cloned from a genomic library by complementation
of a spe-2 mutant. Like other AdoMetDCs, that of Neurospora is derived by cleavage of a proenzyme. The deduced sequence of the Neurospora proenzyme (503 codons) is over 100 codons longer than any other AdoMetDC sequence available in genomic databases. The additional
amino acids are found only in the AdoMetDC of another fungus, Aspergillus nidulans, a cDNA for which we also sequenced. Despite the conserved processing site and four acidic residues required for putrescine
stimulation of human proenzyme processing, putrescine has no effect on the rate (t
0.5∼10 min) of processing of the Neurospora gene product. However, putrescine is absolutely required for activity of the Neurospora enzyme (K
0.5∼100 μM). The abundance of spe-2 mRNA and enzyme activity is regulated 2- to 4-fold by spermidine.
Received: 4 August 1999 / Accepted: 14 February 2000 相似文献
18.
C. T. Yuen J. Garforth T. Besheya R. Jaouhari J. H. McKie A. H. Fairlamb Prof. K. T. Douglas 《Amino acids》1999,17(2):175-183
Summary Kinetic data for alternative substrates of recombinant trypanothione reductase fromTrypanosoma cruzi were measured for a series ofN-substituted-L-cysteinylglycyl-3-dimethylaminopropylamides, in which the cysteineN-substituent was either a variant of the benzyloxycarbonyl group or was L-phenylalanine or L-tryptophan. Replacing the benzylic ether oxygen atom by CH2. or NH had relatively minor effects on kcat, but raised the value of Km, 4.5- and 10-fold, respectively. Similarly, relative to the carbobenzoxy group, anN-L-phenylalanyl orN-L-tryptophanyl replacement on the cysteine hardly altered kcat, but increased Km, values by 16.6 and 7.4 fold, respectively. These observations were consistent with the Km, values referring primarily to binding for this series of nonspecific substrates.Abbreviations DCC
N,N-dicyclohexylcarbodiimide
- dmapa
dimethylaminopropylamine
- DMF
dimethylformamide
- GR
glutathione reductase
- GSSG
glutathione disulphide
- GSH
reduced glutathione
- T[S]2
trypanothione disulphide
- Hbt
hydroxybenzotriazole
- TFA
trifluoroacetic acid
- TLC
thin layer chromatography
- T[SH]2
reduced trypanothione as dithiol
- TR
trypanothione reductase
- Z.cys.gly.dmapa
N-benzyloxycarbonyl-Lcysteinylglycyl-3-dimethylpropylamide 相似文献
19.
The purpose of this study was to identify the seleno-l-methionine (l-SeMet) α,γ-elimination enzyme that catalyzes l-SeMet to generate methylselenol (CH3SeH), a notable intermediate for the metabolism of selenium compounds, in mammalian tissues. The enzyme purified from ICR
mouse liver was separated by one-dimensional gel electrophoresis, and the specific band was subjected to in-gel trypsin digestion
followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometric analysis. In the peptide mass fingerprinting
search, the mass numbers of 14 peptides produced by tryptic digestion of the enzyme were consistent with the theoretical mass
numbers calculated from the amino acid sequence of murine cystathionine γ-lyase (E.C. 4.4.1.1). The peptide sequence tags
search was also performed to obtain the amino acid sequence data of five tryptic peptides. These peptides were significantly
identical to the partial amino acid sequences of cystathionine γ-lyase. This enzyme was clearly shown to catalyze the α, γ-elimination
reaction of l-cystathionine by the enzymological research. The K
m
value for the catalysis of l-cystathionine was 0.81 mM and V
max was. 0.0013 unit/mg protein. These results suggested that cystathionine γ-lyase catalyzes l-SeMet to generate CH3SeH by its α,γ-elimination reaction. 相似文献
20.
Enzymatic reduction of chromate: comparative studies using sulfate-reducing bacteria 总被引:1,自引:0,他引:1
Michel C Brugna M Aubert C Bernadac A Bruschi M 《Applied microbiology and biotechnology》2001,55(1):95-100
Various sulfate-reducing bacteria of the genera Desulfovibrio and Desulfomicrobium were tested and compared for enzymatic reduction of chromate. Our study demonstrated that the ability to reduce chromate
is widespread among sulfate-reducing bacteria. Among them, Desulfomicrobium norvegicum reduced Cr(VI) with the highest reaction rate. This strain grew in the presence of up to 500 μM chromate, but Cr(VI) reduction
in the absence of sulfate was not associated with growth. The presence of chromate induced morphological changes and leakage
of periplasmic proteins into the medium. The ability of isolated polyheme cytochromes c from sulfate- and sulfur-reducing bacteria to reduce chromate was also analyzed. Tetraheme cytochrome c
3(M
r. 13,000) from Desulfomicrobium norvegicum showed twice as much activity as either tetraheme cytochrome c
3 from Desulfovibrio vulgaris strain Hildenborough or triheme cytochrome c
7 from Desulfuromonas acetoxidans. Results with cytochromes c
3 and other c-type cytochromes altered by site-directed mutagenesis indicated that negative redox potential hemes are crucial for metal
reductase activity. The present study also demonstrated that the (Fe) hydrogenase from sulfate-reducing bacteria could reduce
chromate.
Received: 14 April 2000 / Received revision: 6 July 2000 / Accepted: 9 July 2000 相似文献