Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Exponential phase cells of Saccharomyces cerevisiae treated with the superoxide free-radical generating agent menadione (MD; 0.2 mM) for 60 min adapted to become resistant to the lethal effects of a higher concentration of MD (4 mM). Inhibition of protein synthesis by treatment with cycloheximide totally prevented the adaptation to MD, indicating that this is an inducible response completely dependent on protein synthesis; this differs from the situation with peroxide in which only some of the adaptive response is cycloheximide-sensitive. Cells subjected to heat shock (23 to 37 degrees C) or treatment with hydrogen peroxide (H2O2; 0.2 mM, 60 min) became more resistant to 4 mM-MD; however, MD pretreatment did not induce any thermotolerance or resistance to peroxide. These differences between the response to MD and H2O2 were reflected in the results of L-[35S]methionine labelling studies. Using one-dimensional electrophoresis, only one polypeptide (60 kDa) was seen to be induced by 0.2 mM-MD and this was also induced by heat shock but not peroxide stress. With heat shock or peroxide treatment the induction of at least 10 polypeptides was detected using this approach. Using an isogenic petite strain, it was found that functional mitochondria were needed for conferring full resistance to MD, but that induction of the adaptive response was not dependent on mitochondrial function.
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PMID:Saccharomyces cerevisiae has an inducible response to menadione which differs from that to hydrogen peroxide. 847 59

Aspergillus nidulans asexual sporulation (conidiation) is a model system for studying gene regulation and development. The CAN5 cDNA is one of several clones isolated based on transcript induction during conidiation. Here we present the molecular characterization of its corresponding gene, demonstrating that it encodes a developmentally regulated catalase, designated catA. The catA 744-amino-acid-residue polypeptide shows significant identity to other catalases. Its similarity to prokaryotic catalases is greater than to other fungal catalases. catA mRNA is barely detectable in growing mycelia, highly induced during sporulation, and present in isolated spores. However, catA expression is not dependent on the developmental regulatory genes brlA, abaA and wetA. Direct catalase activity determination in native gels revealed the existence of two bands of activity. One of these bands represented the major activity during vegetative growth and was induced during sporulation. The second catalase activity appeared after the induction of sporulation and was the predominant activity in spores. Disruption of catA abolished the major spore catalase without eliminating the vegetative activity, indicating the existence of at least two catalase genes in A. nidulans. catA-disrupted mutants produced spores that were sensitive to H2O2, as compared to wild-type spores. The increase in the activity of the vegetative catalase and the appearance of a second catalase during asexual sporulation is consistent with the occurrence of an oxidative stress during development.
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PMID:catA, a new Aspergillus nidulans gene encoding a developmentally regulated catalase. 859 56

Catalase is an important protective enzyme against H2O2 toxicity. Here, we report the characterization of a Xanthomonas oryzae pv. oryzae catalase gene (katX). The gene was localized and its nucleotide sequence was determined. The gene codes for a 77-kDa polypeptide. The deduced katX amino acid sequence shares regions of high identity with other monofunctional catalases in a range of organisms from bacteria to eukaryotes. The transcriptional regulation of katX was atypical of bacterial monofunctional kat genes. Northern (RNA) analysis showed that katX transcription was highly induced by treatments with low concentrations of menadione, a superoxide generator, and methyl methanesulfonate, a mutagen. It was only weakly induced by H2O2. Unlike in other bacteria, a high level of catalase in Xanthomonas spp. provided protection from the growth-inhibitory and killing effects of H2O2 but not from those of organic peroxides and superoxide generators. Unexpectedly, heterologous expression of katX in Escherichia coli was both growth phase and temperature dependent. Catalase activity in E. coli kat mutants harboring katX on an expression vector was detectable only when the cells entered the stationary phase of growth and at 28 degrees C. The patterns of transcription regulation, heterologous expression, and physiological function of katX are different from previously studied bacterial kat genes.
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PMID:Heterologous growth phase- and temperature-dependent expression and H2O2 toxicity protection of a superoxide-inducible monofunctional catalase gene from Xanthomonas oryzae pv. oryzae. 865 57

Mycobacterium tuberculosis is a natural mutant with inactivated oxidative stress regulatory gene oxyR. This characteristic has been linked to the exquisite sensitivity of M. tuberculosis to isonicotinic acid hydrazide (INH). In the majority of mycobacteria tested, including M. tuberculosis, oxyR is divergently transcribed from ahpC, a gene encoding a homolog of the subunit of alkyl hydroperoxide reductase that carries out substrate peroxide reduction. Here we compared ahpC expression in Mycobacterium smegmatis, a mycobacterium less sensitive to INH, with that in two highly INH sensitive species, M. tuberculosis and Mycobacterium aurum. The ahpC gene of M. smegmatis was cloned and characterized, and the 5' ends of ahpC mRNA were mapped by S1 nuclease protection analysis. M. smegmatis AhpC and eight other polypeptides were inducible by exposure to H2O2 or organic peroxides, as determined by metabolic labeling and Western blot (immunoblot) analysis. In contrast, M. aurum displayed differential induction of only one 18-kDa polypeptide when exposed to organic peroxides. AhpC could not be detected in this organism by immunological means. AhpC was also below detection levels in M. tuberculosis H37Rv. These observations are consistent with the interpretation that ahpC expression and INH sensitivity are inversely correlated in the mycobacterial species tested. In further support of this conclusion, the presence of plasmid-borne ahpC reduced M. smegmatis susceptibility to INH. Interestingly, mutations in the intergenic region between oxyR and ahpC were identified and increased ahpC expression observed in deltakatG M. tuberculosis and Mycobacterium bovis INH(r) strains. We propose that mutations activating ahpC expression may contribute to the emergence of INH(r) strains.
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PMID:Oxidative stress response and its role in sensitivity to isoniazid in mycobacteria: characterization and inducibility of ahpC by peroxides in Mycobacterium smegmatis and lack of expression in M. aurum and M. tuberculosis. 865 66

The glyoxysomes of growing oilseed seedlings produce H2O2, a reactive oxygen species, during the beta-oxidation of lipids stored in the cotyledons. An expression library of dark-grown cotton (Gossypium hirsutm L.) cotyledons was screened with antibodies that recognized a 31-kD glyoxysomal membrane polypeptide. A full-length cDNA clone (1258 bp) was isolated that encodes a 32-kD subunit of ascorbate peroxidase (APX) with a single, putative membrane-spanning region near the C-terminal end of the polypeptide. Internal amino acid sequence analysis of the cotton 31-kD polypeptide verified that this clone encoded this protein. This enzyme, designated gmAPX, was immunocytochemically and enzymatically localized to the glyoxysomal membrane in cotton cotyledons. The activity of monodehydroascorbate reductase, a protein that reduces monodehydroascorbate to ascorbate with NADH, also was detected in these membranes. The co-localization of gmAPX and monodehydroascorbate reductase within the glyoxysomal membrane likely reflects an essential pathway for scavenging reactive oxygen species and also provides a mechanism to regenerate NAD+ for the continued operation of the glyoxylate cycle and beta-oxidation of fatty acids. Immunological cross-reactivity of 30- to 32-kD proteins in glyoxysomal membranes of cucumber, sunflower, castor bean, and cotton indicate that gmAPX is common among oilseed species.
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PMID:Ascorbate peroxidase. A prominent membrane protein in oilseed glyoxysomes. 874 35

We have optimized the conditions under which recombinant Mn peroxidase from the white-rot fungus Phanerochaete chrysosporium can be expressed in Escherichia coli. A bacterial expression vector for the cDNA of Mn peroxidase isozyme H4 (lambda MP1) was constructed (R. E. Whitwam, I. G. Gazarian, and M. Tien, Biochem. Biophys. Res. Commun. 216, 1013-1017, 1995) whose expression in E. coli results in the formation of catalytically inactive polypeptide which can be refolded to active enzyme. The refolded enzyme was purified to homogeneity. Refolding was most efficient in 2 M urea, pH 8.0, and was absolutely dependent upon the presence of CaCl2, hemin, and oxidized glutathione. The recombinant enzyme had the same spectral and kinetic properties as the native fungal enzyme. The Km of recombinant Mn peroxidase for substrates H2O2 and the Mn2+/oxalate complex are 100 and 52 microM, respectively. The kcat as measured by Mn3+/oxalate formation is 450 s-1. These are essentially the same values as seen with the native fungal enzyme. The rate of formation of compound I, the two-electron-oxidized state of the enzyme, is 4.0 x 10(6) M-1 s-1, identical to the rate of the native fungal Mn peroxidase. The reaction of compound I with Mn2+ is too fast to measure at pH 4.5 in the recombinant Mn peroxidase. At a suboptimal pH of 2.5 a rate of 4.2 x 10(4) M-1 s-1 is obtained for the recombinant enzyme. The reaction of compound II, the one-electron-oxidized state of the enzyme, with Mn2+/oxalate has a Kd of 13 microM and a first-order rate constant of 230 s-1 in the recombinant enzyme. These rates are essentially the same as those seen with the native fungal MnP. These results demonstrate that the bacterial expression of recombinant Mn peroxidase is a convenient and efficient system for the expression and characterization of Mn peroxidase.
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PMID:Heterologous expression and reconstitution of fungal Mn peroxidase. 880 85

To discover the molecular properties of two distinct NADH oxidases, corresponding to H2O2-forming oxidase (NOX-1) and H2O-forming oxidase (NOX-2) induced in Streptococcus mutans, for the first step we had cloned and sequenced the nox-1 gene encoding NOX-1. In this paper, a nox-2 gene encoding NOX-2 from S. mutans was cloned, and the nucleotides sequenced. The nox-2 gene comprises 1371 base-pairs, encoding a polypeptide of 457 amino acid residues. The deduced relative molecular mass (M(r) = 49919) agreed with the previous value obtained from the purified NOX-2 protein. The nox-2 gene was expressed in Escherichia coli using its own promoter. Alignment of the NOX-2 protein sequence with that of the NOX-1 showed that the proteins do not significantly resemble each other. Comparisons with the NADH oxidase from Streptococcus faecalis 10C1 yield identities of 41%. The redox-active cysteine in the enzyme from S. faecalis was found to correspond to Cys 44 in the NOX-2.
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PMID:Molecular cloning and sequence analysis of the gene encoding the H2O-forming NADH oxidase from Streptococcus mutans. 882 24

We describe the purification of a H2O-producing NADH oxidase from the protozoan parasite Giardia duodenalis. The enzyme is a monomeric flavoprotein containing flavin adenine dinucleotide in a 1:1 molar ratio with the polypeptide. The NADH oxidase has an apparent molecular mass of 46 kDa and was homogenous as determined by denaturing gel electrophoresis and N-terminal amino acid sequencing. NADPH could substitute for NADH as an electron donor with a K(m) value of 4.2 microM for NADH and 16 microM for NADPH (pH 7.8 at room temperature). With oxygen as the primary electron acceptor under aerobic conditions, the pure enzyme did not produce O.-2 nor H2O2 as stoichiometric products of oxygen reduction, implicating H2O as the end product and obviating the need for superoxide dismutase. The ability to utilise oxygen explains the apparent respiration of the amitochondrial fermentative metabolism of Giardia. Mercurials, flavoantagonists and heavy metals (Cu2+ and Zn2+) inhibited this activity. Under anaerobic conditions the enzyme catalysed electron transfer at lower efficiencies to other electron acceptors including nitroblue tetrazolium, potassium ferricyanide, FAD and FMN, using either NADH or NADPH as electron donors. NADPH, however, was a more efficient electron donor. Cytochrome c was not reduced under any assay conditions used. The enzyme reduced the nitrofuran drugs, furazolidone (an antigiardial) and nitrofurantoin, to their toxic radical forms as determined by EPR. Metronidazole, a nitroimidazole, was not reduced. Pure NADH oxidase did not demonstrate ferredoxin:NAD(P)1 oxidoreductase activity since it could not accept electrons from reduced ferredoxin to regenerate NAD(P)H. The G. duodenalis NADH oxidase may, therefore, function as a terminal oxidase, similar to the mitochondrial cytochrome oxidase, and in the maintenance of an optimum intracellular redox ratio. This report of a flavoenzyme from Giardia places Giardia close to the anaerobic bacteria in evolutionary terms.
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PMID:A H2O-producing NADH oxidase from the protozoan parasite Giardia duodenalis. 889 1

A stress-activated, serine/threonine kinase, p38 (also known as HOG1 or MPK2) belongs to a subgroup of mitogen-activated protein kinase (MAPK) superfamily molecules. An activity to activate p38 (p38 activator activity) as well as p38 activity itself were greatly stimulated by hyperosmolar media in mouse lymphoma L5178Y cells. The activator activity has been purified by sequential chromatography. A 36-kDa polypeptide that was coeluted with the activity in the final chromatography step was identified as MAPK kinase 6 (MAPKK6) by protein microsequencing analysis. Monoclonal and polyclonal antibodies raised against recombinant MAPKK6 recognized specifically the 36-kDa MAPKK6 protein but did not cross-react with MKK3 proteins. The use of these anti-MAPKK6 antibodies revealed that two major peaks of the p38 activator activity in the first chromatography step reside in the activated MAPKK6. Using a genetic screen in yeast, we isolated MKK3b, an alternatively spliced form of MKK3. Like MKK3 and MAPKK6, MKK3b was shown to be a specific activator for p38 and was activated by osmotic shock when expressed in COS7 cells. Immunoblotting analysis revealed that MAPKK6 is expressed highly in HeLa and KB cells and scarcely in PC12 cells, whereas MKK3 and MKK3b are expressed in all cells examined. Immunodepletion of MAPKK6 from the extracts obtained from L5178Y cells and KB cells exposed to hyperosmolar media depleted them of almost all of the p38 activator activity, indicating that MAPKK6 is a major activator for p38 in an osmosensing pathway in these cells. In addition, MAPKK6 was activated strongly by tumor necrosis factor-alpha, H2O2, and okadaic acid and moderately by cycloheximide in KB cells. Thus, there are at least three members of p38 activator, MKK3, MKK3b, and MAPKK6, and MAPKK6 may function as a major activator for p38 when expressed.
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PMID:Purification and identification of a major activator for p38 from osmotically shocked cells. Activation of mitogen-activated protein kinase kinase 6 by osmotic shock, tumor necrosis factor-alpha, and H2O2. 890 Jan 84

Photosystem II (PSII) membranes exhibit catalase and polyphenol oxidase (PPO) activities. Mild heat treatment of PSII membranes for 90 min at 30 degrees C releases most of these enzyme activities into the supernatant, accompanied by a 7-fold activation of PPO. In contrast, mild heat treatment of thylakoid membranes does not release significant amounts of either activity, indicating that both enzymes are bound to the luminal surface of the thylakoid membrane. The heat-released PSII membrane-associated catalase and PPO have been purified and characterized. Catalase activity was correlated with a 63 kDa polypeptide which was purified by batch adsorption to anion-exchange beads followed by gel filtration. The PSII membrane-associated catalase is unstable in solution, probably due to irreversible aggregation. The enzyme was characterized in terms of molecular and subunit size, amino-acid composition, UV-visible absorption, heme content, pH optimum, inhibitor sensitivity, and K(m) value for H2O2. Its properties indicate that the PSII membrane-associated catalase is a luminal thylakoid membrane-bound heme enzyme that has not been identified previously. The residual catalase activity of PSII membranes after mild heat treatment is irreversibly inhibited with 3-amino-1,2,4-triazole, a specific inhibitor of heme catalases, without inhibition of O2-evolution activity. This result indicates that little, if any, of the catalase activity from PSII membranes in the dark is catalyzed by the O2-evolving center of PSII. PPO activity was correlated with a 48 kDa polypeptide. However, the 48 kDa polypeptide and another heat-released polypeptide of 72 kDa have the same N-terminal sequence, which is also identical to that of a known 64 kDa protein [Hind, G., Marshak, D. R., & Coughlan, S. J. (1995) Biochemistry 34, 8157-8164]. During heat treatment of PSII membranes and further manipulations it was found that the 72 kDa polypeptide was largely converted into the 48 kDa polypeptide. Thus, the 72 kDa polypeptide appears to be a latent precursor of the active 48 kDa PPO. The PSII membrane-associated PPO was purified by anion-exchange chromatography and was characterized in terms of substrate specificity, pH optimum, inhibitor sensitivity and native molecular weight. The heat-released PPO appears to be identical to the enzyme previously isolated from spinach thylakoid membranes [Golbeck, J. H., & Cammarata, K. V. (1981) Plant Physiol. 67, 977-984].
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PMID:Isolation and characterization of spinach photosystem II membrane-associated catalase and polyphenol oxidase. 897 99


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