Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.17.1.4 (xanthine dehydrogenase)
1,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The plant molybdenum-cofactor (Moco) and flavin-containing enzymes, xanthine dehydrogenase (XDH; EC 1.2.1.37) and aldehyde oxidase (AO; EC 1.2.3.1) are thought to play important metabolic roles in purine metabolism and hormone biosynthesis, respectively. Their animal counterparts contribute to reactive oxygen species (ROS) production in numerous pathologies and here we examined these enzymes as potential sources of ROS in plants. Novel in-gel assay techniques and Moco sulfurase mutants, lacking a sulfur ligand in their Moco active center, were employed to demonstrate that the native tomato and Arabidopsis XDHs are capable of producing O, but not H2O2, while the animal counterpart was shown to produce both, O and H2O2. Superoxide production was dependent on Moco sulfuration when using hypoxanthine/xanthine but not NADH as substrates. The activity was inhibited by diphenylene iodonium (DPI), a suicide inhibitor of FAD containing enzymes. Analysis of XDH in an Arabidopsis Atxdh1 T-DNA insertion mutant and RNA interference lines revealed loss of O activity, providing direct molecular evidence that plant XDH generates superoxides. Contrary to XDH, AO activity produced only H2O2 dissimilar to native animal AO, that can produce O as well. Surprisingly, H2O2 accumulation was not sensitive to DPI. Plant ROS production and transcript levels of AO and XDH were rapidly upregulated by application of abscisic acid and in water-stressed leaves and roots. These results, supported by in vivo measurement of ROS accumulation, indicate that plant AO and XDH are possible novel sources for ROS increase during water stress.
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PMID:The plant Mo-hydroxylases aldehyde oxidase and xanthine dehydrogenase have distinct reactive oxygen species signatures and are induced by drought and abscisic acid. 1594 99

A barley (Hordeum vulgare L.) mutant (Az34) has been identified with low basal levels of abscisic acid (ABA) and with reduced capacity for producing ABA in response to water stress. The mutation is in a gene controlling the molybdenum cofactor resulting in a pleiotropic deficiency in at least three molybdoenzymes, nitrate reductase, xanthine dehydrogenase, and aldehyde oxidase. The mutant was found to lack aldehyde oxidase activity with several substrates including: (a) ABA aldehyde, a putative precursor of ABA; (b) an acetylenic analog of ABA aldehyde; and (c) heptaldehyde. Elevating the growth temperature from 18 to 26 degrees C caused mutant leaves to wilt and brown. Desiccation of mutant leaves was prevented by applying ABA. These results indicate that ABA biosynthesis at some developmental stages is dependent upon a molybdoenzyme which may be an aldehyde oxidase.
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PMID:Reduced Accumulation of ABA during Water Stress in a Molybdenum Cofactor Mutant of Barley. 1666 35

The molybdenum cofactor (Moco) forms the active site of all eukaryotic molybdenum (Mo) enzymes. Moco consists of molybdenum covalently bound to two sulfur atoms of a unique tricyclic pterin moiety referred to as molybdopterin. Moco is synthesized from GTP by an ancient and conserved biosynthetic pathway that can be divided into four steps involving the biosynthetic intermediates cyclic pyranopterin monophosphate, molybdopterin, and adenylated molybdopterin. In a fifth step, sulfuration or bond formation between Mo and a protein cysteine result in two different catalytic Mo centers. There are four Mo enzymes in plants: (1) nitrate reductase catalyzes the first and rate-limiting step in nitrate assimilation and is structurally similar to the recently identified, (2) peroxisomal sulfite oxidase that detoxifies excessive sulfite. (3) Aldehyde oxidase catalyzes the last step of abscisic acid biosynthesis, and (4) xanthine dehydrogenase is essential for purine degradation and stress response.
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PMID:Molybdenum cofactor biosynthesis and molybdenum enzymes. 1666 76

Aldehyde oxidases are molybdo-flavoenzymes structurally related to xanthine oxidoreductase. They catalyze the oxidation of aldehydes or N-heterocycles of physiological, pharmacological, and toxicological relevance. Rodents are characterized by four aldehyde oxidases as follows: AOX1 and aldehyde oxidase homologs 1-3 (AOH1, AOH2, and AOH3). Humans synthesize a single functional aldehyde oxidase, AOX1. Here we define the structure and the characteristics of the aldehyde oxidase genes and proteins in chicken and dog. The avian genome contains two aldehyde oxidase genes, AOX1 and AOH, mapping to chromosome 7. AOX1 and AOH are structurally very similar and code for proteins whose sequence was deduced from the corresponding cDNAs. AOX1 is the ortholog of the same gene in mammals, whereas AOH represents the likely ancestor of rodent AOH1, AOH2, and AOH3. The dog genome is endowed with two structurally conserved and active aldehyde oxidases clustering on chromosome 37. Cloning of the corresponding cDNAs and tissue distribution studies demonstrate that they are the orthologs of rodent AOH2 and AOH3. The vestiges of dog AOX1 and AOH1 are recognizable upstream of AOH2 and AOH3 on the same chromosome. Comparison of the complement and the structure of the aldehyde oxidase and xanthine oxidoreductase genes in vertebrates and other animal species indicates that they evolved through a series of duplication and inactivation events. Purification of the chicken AOX1 protein to homogeneity from kidney demonstrates that the enzyme possesses retinaldehyde oxidase activity. Unlike humans and most other mammals, dog and chicken are devoid of liver aldehyde oxidase activity.
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PMID:Avian and canine aldehyde oxidases. Novel insights into the biology and evolution of molybdo-flavoenzymes. 1667 19

Molybdenum hydroxylases, which include aldehyde oxidase and xanthine oxidoreductase, are involved in the metabolism of some medicines in humans. They exhibit oxidase activity towards various heterocyclic compounds and aldehydes. The liver cytosol of various mammals also exhibits a significant reductase activity toward nitro, sulfoxide, N-oxide and other moieties, catalyzed by aldehyde oxidase. There is considerable variability of aldehyde oxidase activity in liver cytosol of mammals: humans show the highest activity, rats and mice show low activity, and dogs have no detectable activity. On the other hand, xanthine oxidoreductase activity is present widely among species. Interindividual variation of aldehyde oxidase activity is present in humans. Drug-drug interactions associated with aldehyde oxidase and xanthine oxidoreductase are of potential clinical significance. Drug metabolizing ability of molybdenum hydroxylases and the variation of the activity are described in this review.
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PMID:Drug-metabolizing ability of molybdenum hydroxylases. 1670 28

The transition element molybdenum (Mo) is of essential importance for (nearly) all biological systems as it is required by enzymes catalyzing diverse key reactions in the global carbon, sulfur and nitrogen metabolism. The metal itself is biologically inactive unless it is complexed by a special cofactor. With the exception of bacterial nitrogenase, where Mo is a constituent of the FeMo-cofactor, Mo is bound to a pterin, thus forming the molybdenum cofactor (Moco) which is the active compound at the catalytic site of all other Mo-enzymes. In eukaryotes, the most prominent Mo-enzymes are (1) sulfite oxidase, which catalyzes the final step in the degradation of sulfur-containing amino acids and is involved in detoxifying excess sulfite, (2) xanthine dehydrogenase, which is involved in purine catabolism and reactive oxygen production, (3) aldehyde oxidase, which oxidizes a variety of aldehydes and is essential for the biosynthesis of the phytohormone abscisic acid, and in autotrophic organisms also (4) nitrate reductase, which catalyzes the key step in inorganic nitrogen assimilation. All Mo-enzymes, except plant sulfite oxidase, need at least one more redox active center, many of them involving iron in electron transfer. The biosynthesis of Moco involves the complex interaction of six proteins and is a process of four steps, which also includes iron as well as copper in an indispensable way. Moco as released after synthesis is likely to be distributed to the apoproteins of Mo-enzymes by putative Moco-carrier proteins. Xanthine dehydrogenase and aldehyde oxidase, but not sulfite oxidase and nitrate reductase, require the post-translational sulfuration of their Mo-site for becoming active. This final maturation step is catalyzed by a Moco-sulfurase enzyme, which mobilizes sulfur from l-cysteine in a pyridoxal phosphate-dependent manner as typical for cysteine desulfurases.
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PMID:Cell biology of molybdenum. 1678 86

Chagas' disease (American trypanosomiasis) is an endemic parasitic disease in some areas of Latin America. About 16-18 million persons are infected with the aetiological agent of the disease, Trypanosoma cruzi, and more than 100 million are living at risk of infection. There are different modes of infection: (1) via blood sucking vector insects infected with T. cruzi, accounting for 80-90% of transmission of the disease; (2) via blood transfusion or congenital transmission, accounting for 0.5-8% of transmission; (3) other less common forms of infection, eg, from infected food or drinks or via infected organs used in transplants. The acute phase of the disease can last from weeks to months and typically is asymptomatic or associated with fever and other mild nonspecific manifestations. However, life-threatening myocarditis or meningoencephalitis can occur during the acute phase. The death rate for persons in this phase is about 10%. Approximately 10-50% of the survivors develop chronic Chagas' disease, which is characterized by potentially lethal cardiopathy and megacolon or megaoesophagus. There are two drugs available for the aetiological treatment of Chagas' disease: nifurtimox (Nfx) and benznidazole (Bz). Nfx is a nitrofurane and Bz is a nitroimidazole compound. The use of these drugs to treat the acute phase of the disease is widely accepted. However, their use in the treatment of the chronic phase is controversial. The undesirable side effects of both drugs are a major drawback in their use, frequently forcing the physician to stop treatment. The most frequent adverse effects observed in the use of Nfx are: anorexia, loss of weight, psychic alterations, excitability, sleepiness, digestive manifestations such as nausea or vomiting, and occasionally intestinal colic and diarrhoea. In the case of Bz, skin manifestations are the most notorious (e.g., hypersensitivity, dermatitis with cutaneous eruptions, generalized oedema, fever, lymphoadenopathy, articular and muscular pain), with depression of bone marrow, thrombocytopenic purpura and agranulocytosis being the more severe manifestations. Experimental toxicity studies with Nfx evidenced neurotoxicity, testicular damage, ovarian toxicity, and deleterious effects in adrenal, colon, oesophageal and mammary tissue. In the case of Bz, deleterious effects were observed in adrenals, colon and oesophagus. Bz also inhibits the metabolism of several xenobiotics biotransformed by the cytochrome P450 system and its reactive metabolites react with fetal components in vivo. Both drugs exhibited significant mutagenic effects and were shown to be tumorigenic or carcinogenic in some studies. The toxic side effects of both nitroheterocyclic derivatives require enzymatic reduction of their nitro group. Those processes are fundamentally mediated by cytochrome P450 reductase and cytochrome P450. Other enzymes such as xanthine oxidoreductase or aldehyde oxidase may also be involved.
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PMID:Toxic side effects of drugs used to treat Chagas' disease (American trypanosomiasis). 1693 19

The molybdenum cofactor is essential for the function of sulphite oxidase, xanthine dehydrogenase, and aldehyde oxidase enzymes. Molybdenum cofactor deficiency (MoCD) is a fatal disease resulting in severe neurological damage and death in early childhood. MoCD is an autosomal recessive condition which may mimic ischaemic encephalopathy. Although milder cases with later onset and less severe symptoms have been identified, the classic presentation involves neonatal seizures, progressive encephalopathy and death at an early age. There is currently no effective therapy, and the prognosis is poor. The disorder should be considered in all cases of intractable seizures in the newborn period and infants with clinical and radiological features of ischaemic encephalopathy, especially when no obvious lesion is detected. Blood uric acid measurement should be included in the battery of tests to be performed in all neonates' refractory seizures. We reported here an infant with MoCD who presented with hypoxic ischaemic encephalopathy and identified a novel mutation, c.130C>T in cDNA of the MOCS2 gene from the infant.
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PMID:Molybdenum cofactor deficiency: clinical features in a Turkish patient. 1715 10

One island and one mainland population of Drosophila subobscura were found polymorphic at the XDH (xanthine dehydrogenase) and the AO (aldehyde oxidase) loci. It was observed that one allele at the XDH locus, which has a low frequency in both populations, is nonrandomly associated with the alleles at the AO locus. Two lines of evidence support the thesis that this linkage disequilibrium is due to epistasis rather than random drift: (1) D or r, measures of the disequilibrium, have the same sign and magnitude in both populations. (2) The linkage disequilibrium is not due to inversions. Inversions segregating on the chromosome carrying XDH and AO have been separated into two classes, between which exchange of alleles at the two loci is suppressed. Linkage disequilibrium for XDH and AO was observed within each class. In the absence of any exchange of alleles, these disequilibria must have arisen and been maintained independently. The suggestion is made that the epistatic disequilibrium results from the close structural and physiological relationship which exists between the two enzymes.
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PMID:Evidence for Linkage Disequilibrium Maintained by Selection in Two Natural Populations of DROSOPHILA SUBOBSCURA. 1724 3

The transition element molybdenum (Mo) is an essential micronutrient for plants where it is needed as a catalytically active metal during enzyme catalysis. Four plant enzymes depend on molybdenum: nitrate reductase, sulphite oxidase, xanthine dehydrogenase, and aldehyde oxidase. However, in order to gain biological activity and fulfil its function in enzymes, molybdenum has to be complexed by a pterin compound thus forming the molybdenum cofactor. In this article, the path of molybdenum from its uptake into the cell, via formation of the molybdenum cofactor and its storage, to the final modification of the molybdenum cofactor and its insertion into apo-metalloenzymes will be reviewed.
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PMID:Biology of the molybdenum cofactor. 1735 Dec 49


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