DNA Methylation-Mediated Lowly Expressed AOX1 Promotes Cell Migration and Invasion of Prostate Cancer.

INTRODUCTION: DNA methylation regulates gene transcriptional functions in the pathogenesis of malignant diseases. In prostate cancer, several tumor suppressors are known to be tumor specifically methylated. METHODS: In this study, 450K methylation data and mRNA expression data were accessed from The Cancer Genome Atlas-Prostate Adenocarcinoma database and analyzed bioinformatically. Methylation-specific PCR was used to examine the methylation condition in AOX1 promoter. qRT-PCR was applied to measure the mRNA expression of AOX1. Western blot was employed to detect the expressions of AOX1 and the EMT associated proteins. Transwell and scratch healing assays were used to examine the invasive and migratory abilities of the prostate cancer cells respectively. RESULTS: AOX1 was lowly expressed and hypermethylated in the prostate cancer tissues and cells. Also, AOX1 was downregulated at protein level in prostate cancer cells. Knocking down AOX1 could promote cell migration and invasion in the prostate cancer cells. By using a DNA methylation inhibitor, 5-AzadC was found to promote the expression of AOX1 and reverse the promoting effects of short interfering RNA against AOX1 on cell migration and invasion. CONCLUSION: This study suggested that DNA methylation and low AOX1 level might be biomarkers for prostate cancer.

Aldehyde oxidases mediate plant toxicant susceptibility and fecundity in the red flour beetle, Tribolium castaneum.

Aldehyde oxidases (AOXs) are a group of metabolic enzymes that play critical roles in the degradation of xenobiotics and chemicals. However, the physiological function of this enzyme in insects remains poorly understood. In this study, three TcAOX genes (TcAOX1, TcAOX2, TcAOX3) were identified and characterized from Tribolium castaneum genome. Spatiotemporal expression profiling showed that TcAOX1 expression was most highly expressed at the early pupal stage and was predominantly expressed in the antennae of adults, indicating that TcAOX1 was involved in the degradation of chemical signals; TcAOX2 expression was most highly expressed at the late pupal stage and was mainly expressed in the fat body, epidermis of larvae and adults, respectively; and TcAOX3 expression was in all stages and was primarily expressed in the head of adults. Moreover, the transcripts of TcAOX2 and TcAOX3 were significantly induced after exposure to plant oil, and RNA interference (RNAi) targeting of each of them enhanced the susceptibility of beetles to this plant toxicant, suggesting that these two genes are associated with plant toxicant detoxification. Intriguingly, knockdown of the TcAOX1 led to reductions in female egg-laying but unchanged the hatchability and the development of genital organs, suggesting that this gene may mediate fecundity by effecting the inactivation of chemical signals in T. castaneum. Overall, these results shed new light on the function of AOX genes in insects, and could facilitate the development of research on pest control management.

A plasmonic gold nanofilm-based microfluidic chip for rapid and inexpensive droplet-based photonic PCR.

Polymerase chain reaction (PCR) is a powerful tool for nucleic acid amplification and quantification. However, long thermocycling time is a major limitation of the commercial PCR devices in the point-of-care (POC). Herein, we have developed a rapid droplet-based photonic PCR (dpPCR) system, including a gold (Au) nanofilm-based microfluidic chip and a plasmonic photothermal cycler. The chip is fabricated by adding mineral oil to uncured polydimethylsiloxane (PDMS) to suppress droplet evaporation in PDMS microfluidic chips during PCR thermocycling. A PDMS to gold bonding technique using a double-sided adhesive tape is applied to enhance the bonding strength between the oil-added PDMS and the gold nanofilm. Moreover, the gold nanofilm excited by two light-emitting diodes (LEDs) from the top and bottom sides of the chip provides fast heating of the PCR sample to 230 °C within 100 s. Such a design enables 30 thermal cycles from 60 to 95 °C within 13 min with the average heating and cooling rates of 7.37 ± 0.27 °C/s and 1.91 ± 0.03 °C/s, respectively. The experimental results demonstrate successful PCR amplification of the alcohol oxidase (AOX) gene using the rapid plasmonic photothermal cycler and exhibit the great performance of the microfluidic chip for droplet-based PCR.

Oxidative metabolism and pharmacokinetics of the EGFR inhibitor BIBX1382 in chimeric NOG-TKm30 mice transplanted with human hepatocytes.

The epidermal growth factor receptor inhibitor BIBX1382 has failed in drug development because of poor oral exposure and low bioavailability associated with its extensive metabolism by aldehyde oxidase (AOX) in humans. In this study, we investigated the metabolic profiles and pharmacokinetics of BIBX1382 in chimeric NOG-TKm30 mice with humanized liver (humanized liver mice). After intravenous and oral BIBX1382 administration, increased plasma clearance and decreased oral exposure together with high production of the predominant oxidative metabolite (M1, BIBU1476) and secondary oxidized metabolite (M2) were observed in humanized liver mice. Extensive oxidation rates of BIBX1382 were observed in hepatocytes from humanized liver mice and were suppressed by the typical human AOX1 inhibitors raloxifene and hydralazine. Liver cytosolic fractions from humans, humanized liver mice, cynomolgus monkeys, minipigs, and guinea pigs, but not fractions from dogs, rabbits, rats, and mice, displayed high BIBX1382 clearance and resulted in oxidative metabolite production. These results indicate that humanized liver mice have human-type AOX activity based on the transplanted human liver AOX1 function. Humanized liver mice can be considered an important animal model for understanding the metabolism and pharmacokinetics of AOX drug substrates.

Arabidopsis aldehyde oxidase 3, known to oxidize abscisic aldehyde to abscisic acid, protects leaves from aldehyde toxicity.

The Arabidopsis thaliana aldehyde oxidase 3 (AAO3) catalyzes the oxidation of abscisic aldehyde (ABal) to abscisic acid (ABA). Besides ABal, plants generate other aldehydes that can be toxic above a certain threshold. AAO3 knockout mutants (aao3) exhibited earlier senescence but equivalent relative water content compared with wild-type (WT) during normal growth or upon application of UV-C irradiation. Aldehyde profiling in leaves of 24-day-old plants revealed higher accumulation of acrolein, crotonaldehyde, 3Z-hexenal, hexanal and acetaldehyde in aao3 mutants compared with WT leaves. Similarly, higher levels of acrolein, benzaldehyde, crotonaldehyde, propionaldehyde, trans-2-hexenal and acetaldehyde were accumulated in aao3 mutants upon UV-C irradiation. Aldehydes application to plants hastened profuse senescence symptoms and higher accumulation of aldehydes, such as acrolein, benzaldehyde and 4-hydroxy-2-nonenal, in aao3 mutant leaves as compared with WT. The senescence symptoms included greater decrease in chlorophyll content and increase in transcript expression of the early senescence marker genes, Senescence-Related-Gene1, Stay-Green-Protein2 as well as NAC-LIKE, ACTIVATED-BY AP3/P1. Notably, although aao3 had lower ABA content than WT, members of the ABA-responding genes SnRKs were expressed at similar levels in aao3 and WT. Moreover, the other ABA-deficient mutants [aba2 and 9-cis-poxycarotenoid dioxygenase3-2 (nced3-2), that has functional AAO3] exhibited similar aldehydes accumulation and chlorophyll content like WT under normal growth conditions or UV-C irradiation. These results indicate that the absence of AAO3 oxidation activity and not the lower ABA and its associated function is responsible for the earlier senescence symptoms in aao3 mutant.

Expression of recombinant protease MarP from Mycobacterium tuberculosis in Pichia pastoris and its effect on human monocytes.

OBJECTIVE: Mycobacterial acid-resistant protease (MarP) is a membrane-associated serine protease involved in the survival of Mycobacterium tuberculosis in macrophages; here we produced MarP in the yeast Pichia pastoris and study its involvement in macrophage immune modulation. RESULTS: Pichia pastoris vectors, harboring a full-length or a partial sequence of MarP, were constructed. GS115 clones were selected, and homologous recombination at the AOX1 locus was assessed by PCR. Protein was purified by nickel affinity chromatography, and its effect on the cytokine profile was tested in human monocytes. Only the partial MarP protein (121-397 a.a.) lacking the transmembrane domain was successfully expressed as an N-glycosylated proteolytically active protease. In vitro stimulation of THP-1 cells with MarP promoted the release of TNF-α and IL-10. CONCLUSION: Mycobacterial MarP was successfully expressed in P. pastoris, and it is capable of cytokine release in vitro.

The chemical compound 'Heatin' stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases.

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2-deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound 'Heatin', containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.

Genetic variants of aldehyde oxidase (AOX) 1 in cynomolgus and rhesus macaques.

The cynomolgus macaque is a non-human primate species widely used in drug metabolism studies. Despite the importance of genetic polymorphisms in cytosolic aldehyde oxidase (AOX) 1 in humans, genetic variants have not been investigated in cynomolgus or rhesus macaques.Genetic variants in AOX1 were identified and allele frequencies were assessed using the genomes of 24 cynomolgus and 8 rhesus macaques. The analysis identified 38 non-synonymous variants, some of which were unique to cynomolgus macaques (bred in Cambodia, Indochina, or Indonesia) or rhesus macaques, whereas many variants were shared by the two lineages.Among the variants observed at relatively high frequencies, eight were selected for functional analysis. Recombinant P605L and V1338I AOX1 variants showed substantially lower phthalazine and carbazeran oxidation activities than the wild-type AOX1 protein.In liver cytosolic fractions from cynomolgus and rhesus macaques genotyped for P605L and V1338I AOX1, groups of cytosolic fractions with P605L and/or V1338I AOX1 variants showed significantly lower phthalazine and carbazeran oxidation activities than the wild type.These results indicate that AOX1 is polymorphic in cynomolgus and rhesus macaques, just as it is in humans. Further investigation is needed to reveal the functional significance of these AOX1 variants in drug metabolism.

Production of active recombinant human aldehyde oxidase (AOX) in the baculovirus expression vector system (BEVS) and deployment in a pre-clinical fraction-of-control AOX compound exposure assay.

Human aldehyde oxidase (AOX) has emerged as a key enzyme activity for consideration in modern drug discovery. The enzyme catalyzes the oxidation of a wide variety of compounds, most notably azaheterocyclics that often form the building blocks of small molecule therapeutics. Failure to consider and assess AOX drug exposure early in the drug development cycle can have catastrophic consequences for novel compounds entering the clinic. AOX is a complex molybdopterin-containing iron-sulfur flavoprotein comprised of two identical 150 kDa subunits that has proven difficult to produce in recombinant form, and a commercial source of the purified human enzyme is currently unavailable. Thus, the potential exposure of novel drug development candidates to human AOX metabolism is usually assessed by using extracts of pooled human liver cytosol as a source of the enzyme. This can complicate the assignment of AOX-specific compound exposure due to its low activity and the presence of contaminating enzymes that may have overlapping substrate specificities. Herein is described a two-step process for the isolation of recombinant human AOX dimers to near homogeneity following production in the baculovirus expression vector system (BEVS). The deployment of this BEVS-produced recombinant human AOX as a substitute for human liver extracts in a fraction-of-control AOX compound-exposure screening assay is described. The ability to generate this key enzyme activity readily in a purified recombinant form provides for a more accurate and convenient approach to the assessment of new compound exposure to bona fide AOX drug metabolism.

A candidate aldehyde oxidase in the antennae of the diamondback moth, Plutella xylostella (L.), is potentially involved in the degradation of pheromones, plant-derived volatiles and the detoxification of xenobiotics.

Insect antennae play a fundamental role in perceiving and recognizing a broad spectrum of conventional semiochemicals and host plant-derived odors. As such, genes that are tightly associated with the antennae are thought to have olfactory-related roles related to signal transduction mechanisms. Several mechanisms suggest that enzymatic inactivation could contribute to the signal termination process, such as odorant-degrading enzymes (ODEs). To date, a few ODEs have been identified and characterized in detail in insect herbivores, but little is known about aldehyde oxidases (AOXs); moreover, direct in vivo experimental evidence is needed. AOXs are a major family of metabolic enzymes that oxidize a variety of aromatic aldehydes, and they may also play a significant role in detoxification and degradation of environmental chemical cues. Here, we report on the identification and characterization of a novel cDNA encoding the putative odorant-degrading enzyme, PxylAOX3, from the antennae of the diamondback moth, (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae). The purified recombinant protein showed a wide-range of substrate zymography oxidizing both sex pheromone compounds as well as plant-derived aldehydes with distinct activities. Our data suggest PxylAOX3 might be involved in the degradation of many structurally diverse aldehyde odorants. Furthermore, PxylAOX3 could participate in olfactory neuron protection by inactivation of redundant odorants and xenobiotic detoxification, making it a potential target for pesticide development as well.

Identification and Characterization of Aldehyde Oxidase 5 in the Pheromone Gland of the Silkworm (Lepidoptera: Bombycidae).

Aldehyde oxidases (AOXs) are a subfamily of cytosolic molybdo-flavoenzymes that play critical roles in the detoxification and degradation of chemicals. Active AOXs, such as AOX1 and AOX2, have been identified and functionally analyzed in insect antennae but are rarely reported in other tissues. This is the first study to isolate and characterize the cDNA that encodes aldehyde oxidase 5 (BmAOX5) in the pheromone gland (PG) of the silkworm, Bombyx mori. The size of BmAOX5 cDNA is 3,741 nucleotides and includes an open reading frame, which encodes a protein of 1,246 amino acid residues. The theoretical molecular weight and isoelectric point of BmAOX5 are approximately 138 kDa and 5.58, respectively. BmAOX5 shares a similar primary structure with BmAOX1 and BmAOX2, containing two [2Fe-2S] redox centers, a FAD-binding domain, and a molybdenum cofactor (MoCo)-binding domain. RT-PCR revealed BmAOX5 to be particularly highly expressed in the PG (including ovipositor) of the female silkworm moth, and the expression was further confirmed by in situ hybridization, AOX activity staining, and anti-BmAOX5 western blotting. Further, BmAOX5 was shown to metabolize aromatic aldehydes, such as benzaldehyde, salicylaldehyde, and vanillic aldehyde, and fatty aldehydes, such as heptaldehyde and propionaldehyde. The maximum reaction rate (Vmax) of benzaldehyde as substrate was 21 mU and Km was 1.745 mmol/liter. These results suggested that BmAOX5 in the PG could metabolize aldehydes in the cytoplasm for detoxification or participate in the degradation of aldehyde pheromone substances and odorant compounds to identify mating partners and locate suitable spawning sites.

Meta-analysis based gene expression profiling reveals functional genes in ovarian cancer.

BACKGROUND: Ovarian cancer causes high mortality rate worldwide, and despite numerous attempts, the outcome for patients with ovarian cancer are still not well improved. Microarray-based gene expressional analysis provides with valuable information for discriminating functional genes in ovarian cancer development and progression. However, due to the differences in experimental design, the results varied significantly across individual datasets. METHODS: In the present study, the data of gene expression in ovarian cancer were downloaded from Gene Expression Omnibus (GEO) and 16 studies were included. A meta-analysis based gene expression analysis was performed to identify differentially expressed genes (DEGs). The most differentially expressed genes in our meta-analysis were selected for gene expression and gene function validation. RESULTS: A total of 972 DEGs with P-value < 0.001 were identified in ovarian cancer, including 541 up-regulated genes and 431 down-regulated genes, among which 92 additional DEGs were found as gained DEGs. Top five up- and down-regulated genes were selected for the validation of gene expression profiling. Among these genes, up-regulated CD24 molecule (CD24), SRY (sex determining region Y)-box transcription factor 17 (SOX17), WFDC2, epithelial cell adhesion molecule (EPCAM), innate immunity activator (INAVA), and down-regulated aldehyde oxidase 1 (AOX1) were revealed to be with consistent expressional patterns in clinical patient samples of ovarian cancer. Gene functional analysis demonstrated that up-regulated WFDC2 and INAVA promoted ovarian cancer cell migration, WFDC2 enhanced cell proliferation, while down-regulated AOX1 was functional in inducing cell apoptosis of ovarian cancer. CONCLUSION: Our study shed light on the molecular mechanisms underlying the development of ovarian cancer, and facilitated the understanding of novel diagnostic and therapeutic targets in ovarian cancer.

Site-Directed Mutagenesis at the Molybdenum Pterin Cofactor Site of the Human Aldehyde Oxidase: Interrogating the Kinetic Differences Between Human and Cynomolgus Monkey.

The estimation of the drug clearance by aldehyde oxidase (AO) has been complicated because of this enzyme's atypical kinetics and species and substrate specificity. Since human AO (hAO) and cynomolgus monkey AO (mAO) have a 95.1% sequence identity, cynomolgus monkeys may be the best species for estimating AO clearance in humans. Here, O6-benzylguanine (O6BG) and dantrolene were used under anaerobic conditions, as oxidative and reductive substrates of AO, respectively, to compare and contrast the kinetics of these two species through numerical modeling. Whereas dantrolene reduction followed the same linear kinetics in both species, the oxidation rate of O6BG was also linear in mAO and did not follow the already established biphasic kinetics of hAO. In an attempt to determine why hAO and mAO are kinetically distinct, we have altered the hAO V811 and F885 amino acids at the oxidation site adjacent to the molybdenum pterin cofactor to the corresponding alanine and leucine in mAO, respectively. Although some shift to a more monkey-like kinetics was observed for the V811A mutant, five more mutations around the AO cofactors still need to be investigated for this purpose. In comparing the oxidative and reductive rates of metabolism under anaerobic conditions, we have come to the conclusion that despite having similar rates of reduction (4-fold difference), the oxidation rate in mAO is more than 50-fold slower than hAO. This finding implies that the presence of nonlinearity in AO kinetics is dependent upon the degree of imbalance between the rates of oxidation and reduction in this enzyme. SIGNIFICANCE STATEMENT: Although they have as much as 95.1% sequence identity, human and cynomolgus monkey aldehyde oxidase are kinetically distinct. Therefore, monkeys may not be good estimators of drug clearance in humans.

Aldehyde oxidase 1 promoted the occurrence and development of colorectal cancer by up-regulation of expression of CD133.

Aldehyde oxidase 1 (AOX1) is involved in the detoxification of a variety of aldehydes and nitrogenous heterocyclic compounds. Some reports showed that downregulation of AOX1 was associated with cancers. To probe the mechanism of AOX1 in the development of colorectal cancer, AOX1 expression in clinic specimens and various colorectal cell lines were determined. The results showed that AOX1 expression was downregulated in the cancer genome atlas data, clinic samples and various colorectal cell lines. Moreover, high expression of AOX1 promoted proliferation and invasion and inhibited apoptosis via reactive oxygen species (ROS) production. The histone biomarkers in the promoter of CD133 and regulation proteins were also analyzed using Chip assay and Western blot, which showed that AOX1 promoted the transcription and translation of CD133. In AOX1-/-APCmin/+ mice, the expression levels of CD133, p-PI3K and p-Akt protein in cancer tissues was significantly decreased and the survival rates were greatly increased. In conclusion, we found that AOX1 showed significantly positive correlation with CD133 in vitro and in vivo, indicating that AOX1 could be a potential candidate target for colorectal treatment.

AOX1 and XDH Enzymes Genotyping and its Effect on Clinical Response to Azathioprine in Inflammatory Bowel Disease Patients Among Jordanian Population.

BACKGROUND AND OBJECTIVES: Inflammatory bowel disease (IBD) is a set of chronic inflammatory gastrointestinal disorders, which include ulcerative colitis (UC) and Crohn's disease (CD) that affects many patients worldwide with a peak incidence in early adult life. The immunosuppressant drug Azathioprine (AZA) represents one of the most useful drugs in the management of IBD. It is metabolized by many enzymes like AOX1, and XDH enzymes, the variation in the metabolism of AZA may contribute to inter-individual variation in response to this treatment. This study aims to find out if there is an association between certain AOX1 and XDH polymorphisms and AZA response in Jordanian IBD patients. METHODS: One hundred IBD patients aged between (17-72) years and taking AZA were enrolled and genotyped for AOX13404G, XDH1936C and XDH2107C polymorphisms using DNA Sequencing (Sanger) method. RESULTS AND CONCLUSION: This study revealed that 16% of our patients were non-responders to AZA; they needed an alternative therapy (biological agent) or steroids along with AZA. There was no statistically significant association (p-value>0.05) between the AOX1 3404G, XDH 1936C and XDH 2107C polymorphisms and the response to AZA among Jordanian IBD patients. Finally, the study showed an association between the age of the patient and the response to AZA (p-value=0.013).

A Synthetic Malonyl-CoA Metabolic Oscillator in Komagataella phaffii.

Malonyl-CoA is a key metabolic molecule that participates in a diverse range of physiological responses and can act as a building block for a variety of value-added pharmaceuticals and chemicals. The cytosolic malonyl-CoA concentration is usually very low, and thus dynamic metabolic control of malonyl-CoA variation will aid its stable formation and efficient consumption. We developed a synthetic malonyl-CoA metabolic oscillator in yeast. A synthetic regulatory protein, Prm1-FapR, was constructed by fusing a yeast transcriptional activator, Prm1, with a bacterial malonyl-CoA-sensitive transcription repressor, FapR. Two oppositely regulated biosensors were then engineered. A total of 18 hybrid promoter variants were designed, each carrying the operator sequence (fapO) of FapR and the core promoter of PAOX1 (cPAOX1), which is naturally regulated by Prm1. The promoter activities of these variants, regulated by Prm1-FapR, were tested. Through this process, a sensor for Prm1-FapR/(-52)fapO-PAOX1 carrying an activation/deactivation regulation module was built. Meanwhile, 24 promoter variants of PGAP with fapO inserted were designed and tested using the fusion regulator, giving a sensor for Prm1-FapR/PGAP-(+22) fapO that contained a repression/derepression regulation module. Both sensors were subsequently integrated into a single cell, which exhibited correct metabolic switching of eGFP and mCherry reporters following manipulation of cytosolic malonyl-CoA levels. The Prm1-FapR/(-52)fapO-PAOX1 and the Prm1-FapR/PGAP-(+22)fapO were also used to control the malonyl-CoA source and sink pathways, respectively, for the synthesis of 6-methylsalicylic acid. This finally led to an oscillatory metabolic mode of cytosolic malonyl-CoA. Such a metabolator is useful in exploring potential industrial and biomedical applications not limited by natural cellular behavior.

FSH signaling is involved in affective disorders.

Affective disorders are a set of mental disorders and particularly disrupt the mental health of susceptible women during puberty, pregnancy, parturition and menopause transition, which are characterized by dramatic changes in reproductive hormone profiles. The serum FSH level changes significantly during these periods; yet, the role of FSH in mood regulation is poorly understood. In the current study, FSHR knockout (Fshr-/-) mice displayed enhanced affective disorder behaviors in an open field test and a forced swim test, accompanied by altered gene expression profiles. The differentially expressed genes between Fshr-/- mice and Fshr+/+ mice were enriched in multiple neuroendocrine metabolic pathways. FSHR deletion significantly increased/decreased the mRNA and/or protein expression levels of AOX1, RDH12, HTR3a and HTR4 in mood-mediating brain regions, including the hippocampus and prefrontal cortex. These results reveal that FSH signaling is involved in the development of affective disorders.

Evolution, expression, and substrate specificities of aldehyde oxidase enzymes in eukaryotes.

Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.

A novel mutation in xanthine dehydrogenase in a case with xanthinuria in Hunan province of China.

Xanthinuria is a rare genetic metabolic disorder, the biochemical mechanism of xanthinuria is the disturbance of purine to uric acid metabolism due to the deficiency of xanthine dehydrogenase/xanthine oxidase (XDH/XO) and aldehyde oxidase 1 (AOX1). Xanthinuria has large clinical variability and only about half of all patients have urolithiasis. In this article, we present one xanthinuria case from an unrelated family, which diagnosed by clinical, biochemical and finally confirmed by molecular genetics. One mutation in XDH gene c.2737C > T (p.R913W) and another mutation in SEPT9 gene (c.655C > T (p.R219W)) were identified. To our knowledge, this is the first time that these novel mutations reported in the xanthinuria patients.