Xanthine Dehydrogenase Activity Research Articles

Identification of a xanthinuria type I case with mutations of xanthine dehydrogenase in an Afghan child

Xanthinuria due to xanthine dehydrogenase (XDH) deficiency is a rare genetic disorder characterized by hypouricemia and the accumulation of xanthine in the urine. We have identified an Afghan girl whose xanthinuria could be classified as type I xanthinuria based on an allopurinol loading test. Three mutations were identified in the XDH gene, 141insG, C2729T (T910M) and C3886T (R1296W). Site-directed mutagenesis followed by expression analysis in Escherichia coli revealed that not only the frame shift mutation 141insG impairs XDH activity, but also the missense mutation C2729T, while C3886T resulted in major residual activity of about 50% of the wild type. In this report, a case of xanthinuria type I with mutations of XDH was identified and characterized by expression studies.

Reducing effect of mangiferin on serum uric acid levels in mice

Context: Mangiferin, a natural bioactive xanthone C-glycoside, is widely present in medicinal plants like the leaf of Mangifera indica L. (Anacardiaceae). It has been reported that mangiferin possesses a variety of biological activities, including antidiabetic, hepatoprotective, anti-inflammatory, antioxidant, and anticarcinogenic.Objective: The hypouricemic effect and xanthine oxidoreductase (XOR) inhibitory activity of mangiferin were investigated here for the first time.Materials and methods: The hypouricemic effect of mangiferin was investigated in normal and hyperuricemic mice induced by potassium oxonate. Mangiferin at a dose of 0.75–100.0 mg/kg was given intragastrically to mice. The serum urate levels were determined using the phosphotungstic acid method. The hepatic activities of xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) in hyperuricemic mice were assayed using commercially available kits.Results: The results showed that mangiferin at a dose of 1.5, 3.0, and 6.0 mg/kg significantly reduced the serum urate levels (148.7 ± 37.8, 142.2 ± 44.5, 121.7 ± 21.7 µmmol/L) in hyperuricemic mice, compared with untreated hyperuricemic mice (201.8 ± 71.2 µmmol/L). However, mangiferin did not decrease the serum urate levels in normal mice until mangiferin was up to 100 mg/kg. In addition, the hepatic activities of XDH in hyperuricemic mice were significantly decreased by mangiferin, while no changes of XOD were observed. Acute toxicity study in mice showed that mangiferin was very safe at a dose of up to 25 g/kg.Discussion and conclusion: These findings demonstrate that mangiferin has the potential to be developed as a new therapeutic agent for the treatment of hyperuricemia and gout.

Palm vitamin E reduces catecholamines, xanthine oxidase activity and gastric lesions in rats exposed to water-immersion restraint stress

BackgroundThis study examined the effects of Palm vitamin E (PVE) and α-tocopherol (α-TF) supplementations on adrenalin, noradrenalin, xanthine oxidase plus dehydrogenase (XO + XD) activities and gastric lesions in rats exposed to water-immersion restraint stress (WIRS).MethodsSixty male Sprague–Dawley rats (200-250 g) were randomly divided into three equal sized groups. The control group was given a normal diet, while the treated groups received the same diet with oral supplementation of PVE or α-TF at 60 mg/kg body weight. After the treatment period of 28 days, each group was further subdivided into two groups with 10 rats without exposing them to stress and the other 10 rats were subjected to WIRS for 3.5 hours. Blood samples were taken to measure the adrenalin and noradrenalin levels. The rats were then sacrificed following which the stomach was excised and opened along the greater curvature and examined for lesions and XO + XD activities.ResultsThe rats exposed to WIRS had lesions in their stomach mucosa. Our findings showed that dietary supplementations of PVE and α-TF were able to reduce gastric lesions significantly in comparison to the stressed control group. WIRS increased plasma adrenalin and noradrenalin significantly. PVE and α-TF treatments reduced these parameters significantly compared to the stressed control.ConclusionsSupplementations with either PVE or α-TF reduce the formation of gastric lesions. Their protective effect was related to their abilities to inhibit stress induced elevation of adrenalin and noradrenalin levels as well as through reduction in xanthine oxidase and dehydrogenase activities.

Dual Role of the Molybdenum Cofactor Biosynthesis Protein MOCS3 in tRNA Thiolation and Molybdenum Cofactor Biosynthesis in Humans

We studied two pathways that involve the transfer of persulfide sulfur in humans, molybdenum cofactor biosynthesis and tRNA thiolation. Investigations using human cells showed that the two-domain protein MOCS3 is shared between both pathways. MOCS3 has an N-terminal adenylation domain and a C-terminal rhodanese-like domain. We showed that MOCS3 activates both MOCS2A and URM1 by adenylation and a subsequent sulfur transfer step for the formation of the thiocarboxylate group at the C terminus of each protein. MOCS2A and URM1 are β-grasp fold proteins that contain a highly conserved C-terminal double glycine motif. The role of the terminal glycine of MOCS2A and URM1 was examined for the interaction and the cellular localization with MOCS3. Deletion of the C-terminal glycine of either MOCS2A or URM1 resulted in a loss of interaction with MOCS3. Enhanced cyan fluorescent protein and enhanced yellow fluorescent protein fusions of the proteins were constructed, and the fluorescence resonance energy transfer efficiency was determined by the decrease in the donor lifetime. The cellular localization results showed that extension of the C terminus with an additional glycine of MOCS2A and URM1 altered the localization of MOCS3 from the cytosol to the nucleus.

The response of Mo-hydroxylases and abscisic acid to salinity in wheat genotypes with differing salt tolerances

The differential responses of the wheat cultivars Shi4185 and Yumai47 to salinity were studied. The higher sensitivity of Yumai47 to salinity was linked to a greater growth reduction under salt stress, compared to more salt-tolerant Shi4185. Salinity increased the Na+, proline and superoxide anion radical (O2−) contents in both cultivars. Leaf Na+ content increased less in the more salt-tolerant cultivar Shi4185 than salt-sensitive Yumai47. The proline content increased more significantly in Shi4185 than Yumai47; on the contrary, superoxide anion radical content increased less in Shi4185 than Yumai47. This data indicated that wheat salinity tolerance can be increased by controlling Na+ transport from the root to shoot, associated with higher osmotic adjustment capability and antioxidant activity. Although salinity increased aldehyde oxidase (AO) activity and abscisic acid (ABA) content in the leaves and roots of both cultivars following the addition of NaCl to the growth medium, AO and ABA increased more in the salt-sensitive cultivar Yumai47 than the more salt-tolerant cultivar Shi4185. Xanthine dehydrogenase (XDH) activity in the leaves of both cultivars increased with increasing concentrations of NaCl; however, leaf XDH activity increased more significantly in Yumai47 than Shi4185. Root XDH activity in Shi4185 decreased with increasing NaCl concentrations, whereas salinity induced an increased root XDH activity in Yumai47. The involvement of AO and XDH enzymatic activities and altered ABA content in the response mechanisms of wheat to salinity are discussed herein.

All-trans Arachidonic acid generates reactive oxygen species via xanthine dehydrogenase/xanthine oxidase interconversion in the rat liver cytosol in vitro

We previously reported that the all-cis isomer of arachidonic acid, the most naturally occurring isoform of this fatty acid, reduced cuprous copper ion-induced conversion of xanthine dehydrogenase into its reactive oxygen species generating form, xanthine oxidase. In the present study, the effects of all-trans isomer of arachidonic acid, in comparison with cis isomer of arachidonic acid, on the xanthine dehydrogenase/xanthine oxidase interconversion were explored. cis isomer of arachidonic acid alone did not have any significant effect on the activities of xanthine dehydrogenase and xanthine oxidase, but it inhibited the cuprous copper ion-induced conversion of xanthine dehydrogenase to xanthine oxidase in rat liver cytosol in vitro. In contrast, trans isomer of arachidonic acid elicited an increase in xanthine oxidase activity concomitant with a decrease in xanthine dehydrogenase activity, and further potentiated the cuprous copper ion-induced xanthine dehydrogenase/xanthine oxidase interconversion. In primary rat hepatocyte cultures, trans isomer of arachidonic acid increased 2',7'-dichlorofluorescein-fluorescence intensity in the cytosolic fraction from 2',7'-dichlorodihydrofluorescein, an indicator of reactive oxygen species generation. The pretreatment of allopurinol, an xanthine oxidase inhibitor, diminished the trans isomer of arachidonic acid-induced increase in the 2',7'-dichlorofluorescein-fluorescence intensity, indicating the role of xanthine dehydrogenase/xanthine oxidase in mediating trans isomer of arachidonic acid-induced reactive oxygen species generation. These observations suggest that, in contrast to all-cis arachidonic acid, all-trans arachidonic acid has the potential to enhance reactive oxygen species generation via xanthine dehydrogenase/xanthine oxidase interconversion in the liver cytosol in vitro.

The Antioxidant Role of Mulberry (Morus alba L.) Fruits in Ameliorating the Oxidative Stress Induced in γ-Irradiated Male Rats

Based on the radioprotective effect of substance possessing antioxidant effect previously reported, it was hypothesized that mulberry fruit, a substance possessing antioxidant activity, might be able to protect against oxidative stress induced by γ-rays. Gamma-irradiation (2.5 Gy×3 delivered every other day) resulted in a significant decrease in hepatic Glutathione contents (GSH), Xanthine Dehydrogenase (XDH), Superoxides Dismutase (SOD) and Catalase (CAT) activity, the level of insulin and testosteroneC as well as the concentration of High Density Lipoprotein-Cholesterol (HDL-C). Moreover, a remarkable increase in the Malondialdehyde (MDA) concentration, xanthine oxidase activity, the activity of some liver enzymes, the level of glucose and the concentrations of Total Cholesterol (TC), Triglycerides (TG), low density- and very low density lipoprotein-cholesterol was observed in γ-irradiated rats. In contrast, administration of Mulberry Fruit Powder (MFP) to γ-irradiated rats was found to offer protection against γ-irradiation induced oxidative stress, by elevating the activity of antioxidant enzymes, enhancing liver function, in addition to improving the lipid metabolism. All results in this study suggested that mulberry fruit had high potential to be developed as radio protective agent.

Differential expression of cysteine desulfurases in soybean

BackgroundIron-sulfur [Fe-S] clusters are prosthetic groups required to sustain fundamental life processes including electron transfer, metabolic reactions, sensing, signaling, gene regulation and stabilization of protein structures. In plants, the biogenesis of Fe-S protein is compartmentalized and adapted to specific needs of the cell. Many environmental factors affect plant development and limit productivity and geographical distribution. The impact of these limiting factors is particularly relevant for major crops, such as soybean, which has worldwide economic importance.ResultsHere we analyze the transcriptional profile of the soybean cysteine desulfurases NFS1, NFS2 and ISD11 genes, involved in the biogenesis of [Fe-S] clusters, by quantitative RT-PCR. NFS1, ISD11 and NFS2 encoding two mitochondrial and one plastid located proteins, respectively, are duplicated and showed distinct transcript levels considering tissue and stress response. NFS1 and ISD11 are highly expressed in roots, whereas NFS2 showed no differential expression in tissues. Cold-treated plants showed a decrease in NFS2 and ISD11 transcript levels in roots, and an increased expression of NFS1 and ISD11 genes in leaves. Plants treated with salicylic acid exhibited increased NFS1 transcript levels in roots but lower levels in leaves. In silico analysis of promoter regions indicated the presence of different cis-elements in cysteine desulfurase genes, in good agreement with differential expression of each locus. Our data also showed that increasing of transcript levels of mitochondrial genes, NFS1/ISD11, are associated with higher activities of aldehyde oxidase and xanthine dehydrogenase, two cytosolic Fe-S proteins.ConclusionsOur results suggest a relationship between gene expression pattern, biochemical effects, and transcription factor binding sites in promoter regions of cysteine desulfurase genes. Moreover, data show proportionality between NFS1 and ISD11 genes expression.

Hyperoxia during colon surgery is associated with a reduction of xanthine oxidase activity and oxidative stress in colonic mucosa

BackgroundGut manipulation during surgery may induce local oxidative stress. Supplemental inspired oxygen increases arterial and tissue oxygen partial pressures. This study examined whether a 0.80 fraction of inspired oxygen (FiO2) attenuates the oxidative stress, reducing xanthine oxidase (XO) activity in colonic mucosa as a possible mechanism during colon surgery.MethodsTwenty-four cancer patients who underwent elective colon resection were randomly assigned to either 0.30 FiO2 or 0.80 FiO2 during surgery. Malondialdehyde (MDA) and oxidized glutathione (GSSG) levels were measured in blood plasma. We also determined the enzymatic activities of XO and xanthine dehydrogenase (XDH) in the colonic mucosa after resection of the piece of colon.ResultsOxygen partial pressure in arterial blood was higher in the 0.80 FiO2 group than in the 0.30 FiO2 group (P < 0.001). MDA and GSSG levels measured in blood plasma as well as MDA measured in colonic mucosa were lower in the 0.80 FiO2 group than in the 0.30 FiO2 group. Otherwise, XO enzymatic activity and XO/(XO + XDH) ratio in colonic mucosa were lower in the 0.80 FiO2 group than in the 0.30 FiO2 group.ConclusionsXO may be a major source of reactive oxygen species in patients during colon surgery. Inspiring 0.80 oxygen during colon surgery increases arterial partial pressure and this treatment was associated with reduced XO activity and levels of oxidative stress in colonic mucosa.

A sirA-like gene, sirA2, is essential for 3-succinoyl-pyridine metabolism in the newly isolated nicotine-degrading Pseudomonas sp. HZN6 strain

A novel nicotine-degrading Pseudomonas sp. strain, HZN6, was isolated from a pesticide-wastewater treatment facility in Hangzhou. The strain could grow on nicotine as its sole source of carbon, nitrogen, and energy. The strain's main intermediate metabolites were determined to be pseudooxynicotine, 3-succinoyl-pyridine (SP), and 6-hydroxy-3-succinoyl-pyridine (HSP). A Tn5 transposon mutant was generated in which the degradation pathway was blocked at the SP. A 4,583-bp DNA fragment flanking the transposon insertion site was obtained through self-formed adaptor PCR and analyzed. The mutant gene orfC displays 89% deduced amino acid sequence identity with the sirA-like gene (sirA2, a sulfurtransferase homologue gene) of Pseudomonas stutzeri A1501. The orfC-disrupted strain lost the ability to degrade SP, and the complementation strains with the orfC from the Pseudomonas sp. HZN6 and the sirA2 (PP_1233) from Pseudomonas putida KT2440 recovered the degradation ability. Though the orfC-disrupted strain also lost the xanthine dehydrogenase activity, the effects of tungsten on the degradation of SP and hypoxanthine revealed that the hydroxylation of SP to HSP was not a xanthine dehydrogenase type. These results demonstrated that the orfC gene was essential for the SP metabolism involved in the nicotine metabolic pathway in the Pseudomonas sp. HZN6 strain. This study might advance the understanding of the nicotine metabolic mechanism in Pseudomonas.

Antihyperuricemic and diuretic effects of procyanidins extracted from Crataegus monogyna

Background and objectives: Data indicated that procyanidins extracted from grape seeds has uric acid-lowering effects in mice, however the hypouricaemic effect of procyanidins was not accompanied with changes in enzymatic activities of xanthine dehydrogenase and xanthine oxidase. This study was designed to investigate the effect of procyanidins extracted from Crataegus monogyna on serum uric acid, adenosine deaminase (ADA), 5nucleotidase, xanthine oxidase, and renal function on normal and potassium oxonate induced hyperuricemic rats. Methods: Thirty female albino rats were divided into three groups. The first group included 18 rats pretreated with the uricase inhibitor potassium oxonate (250 mg/kg, i.p.), served as an animal model for hyperuricemia. The rat models were divided into three subgroups, each subgroup having six rats. The first subgroup served as a normal control. Subgroup 2 received a single daily dose (100 mg/kg p.o) of procyanidins for 7 days. The third subgroup received daily dose (50 mg/kg p.o) of allopurinol for 7 days as positive control. The second group included six rats received only water as a vehicle. The serum uric acid, xanthine oxidase, adenosine deaminase (ADA) and 5-nucleotidase levels were measured and compared to those in normal untreated control group. The Third group included six normal rats received a single dose of Procyanidins (50 mg/kg body weight; i.v.) to study the renal effects of procyanidins.. Results: A single daily dose (100 mg/kg PO) of procyanidins for 7 days significantly reduced serum levels of uric acid, ADA and 5’-nucleotidase, without detectable effects on the level of xanthine oxidase in hyperuricemic rats. Intravenous infusion of a single dose of procyanidins (50 mg/kg i.v) produced marked increases in urinary Na + excretion (4.8 folds) and urine flow (2.6 folds) accompanied by insignificant change of potassium excretion in the rats. Conclusion: The reduction in serum uric acid most probably is due to inhibiting enzymes, ADA and 5-nucleotidase. The antihyperuricemic and diuretic effects of procyanidins recommended it as a good drug for the treatment of gout and renal uric acid calculi.

A Selenium-Dependent Xanthine Dehydrogenase Triggers Biofilm Proliferation inEnterococcus faecalisthrough Oxidant Production

Selenium has been shown to be present as a labile cofactor in a small class of molybdenum hydroxylase enzymes in several species of clostridia that specialize in the fermentation of purines and pyrimidines. This labile cofactor is poorly understood, yet recent bioinformatic studies have suggested that Enterococcus faecalis could serve as a model system to better understand the way in which this enzyme cofactor is built and the role of these metalloenzymes in the physiology of the organism. An mRNA that encodes a predicted selenium-dependent molybdenum hydroxylase (SDMH) has also been shown to be specifically increased during the transition from planktonic growth to biofilm growth. Based on these studies, we examined whether this organism produces an SDMH and probed whether selenoproteins may play a role in biofilm physiology. We observed a substantial increase in biofilm density upon the addition of uric acid to cells grown in a defined culture medium, but only when molybdate (Mo) and selenite (Se) were also added. We also observed a significant increase in biofilm density in cells cultured in tryptic soy broth with 1% glucose (TSBG) when selenite was added. In-frame deletion of selD, which encodes selenophosphate synthetase, also blocked biofilm formation that occurred upon addition of selenium. Moreover, mutation in the gene encoding the molybdoenzyme (xdh) prevented the induction of biofilm proliferation upon supplementation with selenium. Tungstate or auranofin addition also blocked this enhanced biofilm density, likely through inhibition of molybdenum or selenium cofactor synthesis. A large protein complex labeled with (75)Se is present in higher concentrations in biofilms than in planktonic cells, and the same complex is formed in TSBG. Xanthine dehydrogenase activity correlates with the presence of this labile selenoprotein complex and is absent in a selD or an xdh mutant. Enhanced biofilm density correlates strongly with higher levels of extracellular peroxide, which is produced upon the addition of selenite to TSBG. Peroxide levels are not increased in either the selD or the xdh mutant upon addition of selenite. Extracellular superoxide production, a phenomenon well established to be linked to clinical isolates, is abolished in both mutant strains. Taken together, these data provide evidence that an SDMH is involved in biofilm formation in Enterococcus faecalis, contributing to oxidant production either directly or alternatively through its involvement in redox-dependent processes linked to oxidant production.

In vitro (?-Glucosidase and ?-Amylase Inhibition) and in vivo Antidiabetic Property of Phytic Acid (IP6) in Streptozotocin-Nicotinamide-Induced Type 2 Diabetes Mellitus (NIDDM) in Rats

Phytic acid, inositol hexaphosphate (IP6) a natural plant constituent and antioxidant exhibits protective action in carcinogenesis, Alzheimer's, hypercholesterolemia, diabetes and inflammations when taken in diet. The aim of this study is to evaluate effect of phytic acid in streptozotocin (STZ)-nicotinamide-induced type 2 diabetes in rats. The STZ-nicotinamide induced diabetic rats were orally treated with vehicle (2%w/v Tween 80), glimepiride (2.5 mg/kg) and IP6 (650 mg/kg) for 28 days. The blood glucose level, body weight, glycosylated haemoglobin (HbA1C), lipid profile, lipid peroxidation, antioxidant status (liver and small intestine) was measured and compared with control. Xanthine dehydrogenase (XDH) and xanthine (XO) activity was measured in small intestine of diabetic rats. In vitro inhibition of carbohydrate digestive enzymes (α-glucosidase and α-amylase) was also determined. IP6, significantly (P<0.01) reduced glucose level, HbA1C, lipid profile and lipid peroxidation, and increased body weight, high density lipoprotein level and antioxidant status in liver and small intestine. Decrease in XO and increase in XDH activity was observed in treatment groups compared to diabetic control. Dose dependent inhibition of α-glucosidase and (α-amylase activity was observed for phytic acid when compared to standard drug acarbose. These results clearly indicate that IP6 possess promising in vitro and in vivo antidiabetic activity.

Investigation of the Oxidative Effect of Chronic Hyperammonemia on the Kidney and the Possible Protective Effect of Allopurinol

Although there have been many studies on this topic, the molecular mechanism of the toxic effects of hyperammonemia on cells has not yet been fully explained. Recent studies have held oxidative stress mechanisms responsible for hyperammonemia-induced cell damage. Kidney functions are affected in diseases associated with an increase in ammonia in the blood. Our study tries to determine whether oxidative stress mechanisms are responsible for kidney damage in chronic hyperammonemia. We also investigated whether kidney damage is dependent on possible reactive oxygen products associated with the xanthine oxidase (XO) enzyme and whether the possible association can be inhibited with allopurinol, an XO enzyme inhibitor. The study took into consideration the enzyme activities of XO, xanthine dehydrogenase (XDH), superoxide dismutase (SOD), glutathione-S-transferase (GST), as well as protein thiol (P–SH) and malondialdehyde (MDA) levels. The data found demonstrated that chronic hyperammonemia had oxidative stress effects on the kidney, and that kidney XO and XDH activity changed. However, it was not possible to inhibit this oxidative stress in the kidney using allopurinol. Thus, we could not conclude that oxidative stress is an XO‐dependent mechanism. The outcomes of the study suggested that this oxidative situation arising in hyperammonemia occurred through a mechanism other than the XO enzyme.

Sildenafil protects human mammary epithelial cells against ROS production induced by estradiol.

Several studies suggest that xanthine dehydrogenase (XDH) and its oxidase form (XO) play an important role in various types of ischemic and vascular injuries. Recently, we have demonstrated that estradiol (E2) induces a significant decrease of the expression and activity of XDH and of its conversion to XO in human mammary epithelial cells. E2 is known to induce upregulation of eNOS gene expression in aortic endothelial cells. Because the XO-derived O2·- combines with ·NO to yield ONOO-, and considering that ONOO- converts XDH to XO, the resulting increase of XO activity and reactive oxygen species production would eventually lead to a further increase of ONOO- production, thus creating a vicious cycle of oxidative stress. Our previous study has indicated that sildenafil has a protective effect on human mammary epithelial cells as a consequence of XO inhibition and of the resulting decrease of free oxygen radicals that can impair the expression of NADPH oxidase and type 5 phosphodiesterase (PDE-5). In the present study, we report that the dual inhibitory effect exerted by sildenafil on both XO and PDE-5 is a consequence of a structural modification induced by O2·-, also consisting of the release of a piperazine group that could in turn inhibit the XO enzyme.

Molybdenum as an essential element for improving total yield in seawater-grown Salicornia europaea L.

The growth of crop plants on full-strength seawater constitutes a major challenge because of the high salt content and the limited availability of essential microelements such as molybdenum. For cultivation of the halophyte Salicornia as seawater-grown crop, the effect of molybdate application on total yield production and the activities of the two molybdenum containing enzymes, nitrate reductase (NR) and xanthine dehydrogenase (XDH) was investigated. Increasing molybdate levels in the growth medium supplemented with nitrate or ammonium enhanced yield during multiple shoot removal. Similarly, NR and XDH activities were enhanced with increasing molybdate, indicating that the activity of both enzymes may play an important role in facilitating yield accumulation. Notably, XDH activity in the roots was high and the levels of ureides were low, whereas in the shoot tips ureides were higher and XDH activity was lower. Considering that XDH is a key enzyme in the biosynthesis of the low C/N ratio ureides, these suggest a source–sink relationship between the roots and shoot tips for efficient transport of root-generated ureides to the young growing shoot tips. Our results imply that the supply of molybdenum to Salicornia grown in seawater enhances plant biomass accumulation by increasing the activities of NR and XDH, thereby stimulating a more efficient remobilization of ureides to the newly grown shoot tips after periodic shoot removal.

Deficiency in xanthine dehydrogenase activity in the og and ogt mutants of the silkworm, Bombyx mori

Deficiency in xanthine dehydrogenase activity in the og and ogt mutants of the silkworm, Bombyx mori

Bisphenol A 3,4-quinone induces the conversion of xanthine dehydrogenase into oxidase in vitro

In the present study, we assessed the influence of bisphenol A (BPA) and bisphenol A 3,4-quinone (BPAQ) on the conversion of xanthine dehydrogenase (XD) into xanthine oxidase (XO) in the rat liver in vitro. BPA up to 100 μmol/L did not affect the XO and XD activities in the partially purified cytosolic fraction from rat liver, whereas BPAQ (2–10 μmol/L) dose-dependently enhanced the XO activity concomitant with a decrease in the XD activity, implying that BPAQ, but not BPA, can convert XD into the reactive oxygen species (ROS) producing the form XO. Furthermore, it was found that BPAQ could increase the generation of ROS and oxidize the guanine moiety of deoxyguanosine in the DNA of primary rat hepatocyte cultures. These results suggest that BPAQ has the potential to convert XD into XO in the liver, which in turn may lead to ROS generation and oxidative DNA damage in this region.

Reparatory and preventive effects of oriental herb extract mixture (OHEM) on hyperuricemia and gout

Gout (also called metabolic arthritis) is a disease created by a buildup of uric acid inside of the blood and other tissue such as liver and kidney. Research to develop alternative medicines for hyperuricemia and gout has focused on the screening of natural substances due to the adverse side effects of allopurinol, which remains the only prescription for the disease. The oriental herb extract mixture (OHEM) is a mixture of water extract of Korean native herbs, Lonicera japonica, Cassia obtusifolia L., Adenophora triphylla var. japonica, Rhynchosia nulubilis, and Glycyrrhiza glabra. OHEM was found to possess xanthine oxidase (XO) inhibitory activity as well as a high level of functional phytochemicals such as polyphenols and flavonoids. The toxicity of OHEM was barely detected in both cell culture and animal study. XO and xanthine dehydrogenase (XDH) activities in liver tissues were reduced by 95% following OHEM pretreatment. The oral administration of OHEM also demonstrated a protective effect on liver tissues against damage caused by the induction of hyperuricemia. Indeed, the size of gouty edema was significantly reduced (62%) following oral OHEM pretreatment. These observations demonstrated the positive effect of OHEM pretreatment on the prevention and treatment of hyperuricemia and gout.

A Novel Role for Arabidopsis Mitochondrial ABC Transporter ATM3 in Molybdenum Cofactor Biosynthesis

The molybdenum cofactor (Moco) is a prosthetic group required by a number of enzymes, such as nitrate reductase, sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Its biosynthesis in eukaryotes can be divided into four steps, of which the last three are proposed to occur in the cytosol. Here, we report that the mitochondrial ABC transporter ATM3, previously implicated in the maturation of extramitochondrial iron-sulfur proteins, has a crucial role also in Moco biosynthesis. In ATM3 insertion mutants of Arabidopsis thaliana, the activities of nitrate reductase and sulfite oxidase were decreased to approximately 50%, whereas the activities of xanthine dehydrogenase and aldehyde oxidase, whose activities also depend on iron-sulfur clusters, were virtually undetectable. Moreover, atm3 mutants accumulated cyclic pyranopterin monophosphate, the first intermediate of Moco biosynthesis, but showed decreased amounts of Moco. Specific antibodies against the Moco biosynthesis proteins CNX2 and CNX3 showed that the first step of Moco biosynthesis is localized in the mitochondrial matrix. Together with the observation that cyclic pyranopterin monophosphate accumulated in purified mitochondria, particularly in atm3 mutants, our data suggest that mitochondria and the ABC transporter ATM3 have a novel role in the biosynthesis of Moco.