Molybdenum-containing hydroxylases

Multiple Roles of a Conserved Glutamate Residue for Unique Biophysical Properties in a New Group of Microbial Rhodopsins Homologous to TAT Rhodopsin

TAT rhodopsin, a microbial rhodopsin found in the marine SAR11 bacterium HIMB114, uniquely possesses a Thr-Ala-Thr (TAT) motif in the third transmembrane helix. Because of a low pKa value of the retinal Schiff base (RSB), TAT rhodopsin exhibits both a visible light-absorbing state with the protonated RSB and a UV-absorbing state with the deprotonated RSB at a neutral pH. The UV-absorbing state, in contrast to the visible light-absorbing one, converts to a long-lived photointermediate upon light absorption, implying that TAT rhodopsin functions as a pH-dependent light sensor. Despite detailed biophysical characterization and mechanistic studies on the TAT rhodopsin, it has been unknown whether other proteins with similarly unusual features exist. Here, we identified several new rhodopsin genes homologous to the TAT rhodopsin of HIMB114 (TATHIMB) from metagenomic data. Based on the absorption spectra of expressed proteins from these genes with visible and UV peaks similar to that of TATHIMB, they were classified as Twin-peaked Rhodopsin (TwR) family. TwR genes form a gene cluster with a set of 13 ORFs conserved in subclade IIIa of SAR11 bacteria. A glutamic acid in the second transmembrane helix, Glu54, is conserved in all of the TwRs. We investigated E54Q mutants of two TwRs and revealed that Glu54 plays critical roles in regulating the RSB pKa, oligomer formation, and the efficient photoreaction of the UV-absorbing state. The discovery of novel TwRs enables us to study the universality and individuality of the characteristics revealed so far in the original TATHIMB and contributes to further studies on mechanisms of unique properties of TwRs.

Xanthine Oxidoreductase in the Pathogenesis of Endothelial Dysfunction: An Update

Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in the formation of uric acid (UA) and is involved in the generation of reactive oxygen species (ROS). Overproduction of ROS has been linked to the pathogenesis of hypertension, atherosclerosis, and cardiovascular disease, with multiple studies over the last 30 years demonstrating that XOR inhibition is beneficial. The involvement of XOR and its constituents in the advancement of chronic inflammation and ROS, which are responsible for endothelial dysfunction, is the focus of this evidence-based review. An overabundance of XOR products and ROS appears to drive the inflammatory response, resulting in significant endothelium damage. It has also been demonstrated that XOR activity and ED are connected. Diabetes, hypertension, and cardiovascular disease are all associated with endothelial dysfunction. ROS mainly modifies the activity of vascular cells and can be important in normal vascular physiology as well as the development of vascular disease. Suppressing XOR activity appears to decrease endothelial dysfunction, probably because it lessens the generation of reactive oxygen species and the oxidative stress brought on by XOR. Although there has long been a link between higher vascular XOR activity and worse clinical outcomes, new research suggests a different picture in which positive results are mediated by XOR enzymatic activity. Here in this study, we aimed to review the association between XOR and vascular endothelial dysfunction. The prevention and treatment approaches against vascular endothelial dysfunction in atherosclerotic disease.

Hyperuricemia remission after colorectal cancer surgery for colorectal cancer patients

The purpose of this study was to investigate whether patients with colorectal cancer (CRC) combined with hyperuricemia remitted 1 year after CRC surgery. CRC patients combined with hyperuricemia who underwent radical surgery were included from a single clinical center from Jan 2016 to Dec 2021. Baseline characteristics was compared between the remission group and the non-remission group. Multivariate logistic regression was used to find the possible predictive factors of hyperuricemia remission. A total of 91 patients were included for data analysis, retrospectively. There were 34 (37.4%) patients in the remission group and 57 (62.6%) patients in the non-remission group. The mean preoperative weight and body mass index (BMI) were 61.2 ± 10.7 (kg) and 24.1 ± 3.3 (kg/m2). 21 (23.1%) patients had a history of drinking. We found that the weight and BMI were not significantly different before and 1 year after CRC surgery (P > 0.05). In contrast, uric acid values were significantly decreased (P < 0.01). Meanwhile, the outcomes showed there were no significant differences in the baseline characteristics between the remission and non-remission groups (P > 0.05). According to multivariate logistic regression, we found that the history of drinking was a predictive factor of hyperuricemia remission (OR = 0.046, 95% CI 0.005-0.475, P = 0.010). CRC patients with hyperuricemia had a 37.4% remission from hyperuricemia 1 year after CRC surgery. Tumor location, tumor stage, and tumor size did not predict the remission of hyperuricemia. Notably, the history of drinking was a predictive factor of hyperuricemia remission.

Investigation of the Inhibition Mechanism of Xanthine Oxidoreductase by Oxipurinol: A Computational Study

Xanthine oxidoreductase (XOR) is an enzyme found in various organisms. It converts hypoxanthine to xanthine and urate, which are crucial steps in purine elimination in humans. Elevated uric acid levels can lead to conditions like gout and hyperuricemia. Therefore, there is significant interest in developing drugs that target XOR for treating these conditions and other diseases. Oxipurinol, an analogue of xanthine, is a well-known inhibitor of XOR. Crystallographic studies have revealed that oxipurinol directly binds to the molybdenum cofactor (MoCo) in XOR. However, the precise details of the inhibition mechanism are still unclear, which would be valuable for designing more effective drugs with similar inhibitory functions. In this study, molecular dynamics and quantum mechanics/molecular mechanics calculations are employed to investigate the inhibition mechanism of XOR by oxipurinol. The study examines the structural and dynamic effects of oxipurinol on the pre-catalytic structure of the metabolite-bound system. Our results provide insights on the reaction mechanism catalyzed by the MoCo center in the active site, which aligns well with experimental findings. Furthermore, the results provide insights into the residues surrounding the active site and propose an alternative mechanism for developing alternative covalent inhibitors.

A consensual machine-learning-assisted QSAR model for effective bioactivity prediction of xanthine oxidase inhibitors using molecular fingerprints

Xanthine oxidase inhibitors (XOIs) have been widely studied due to the promising potential as safe and effective therapeutics in hyperuricemia and gout. Currently, available XOI molecules have been developed from different experiments but they are with the wide structure diversity and significant varying bioactivities. So it is of great practical significance to present a consensual QSAR model for effective bioactivity prediction of XOIs based on a systematic compiling of these XOIs across different experiments. In this work, 249 XOIs belonging to 16 scaffolds were collected and were integrated into a consensual dataset by introducing the concept of IC₅₀ values relative to allopurinol (RIC₅₀). Here, extended connectivity fingerprints (ECFPs) were employed to represent XOI molecules. By performing effective feature selection by machine-learning method, 54 crucial fingerprints were indicated to be valuable for predicting the inhibitory potency (IP) of XOIs. The optimal predictor yields the promising performance by different cross-validation tests. Besides, an external validation of 43 XOIs and a case study on febuxostat also provide satisfactory results, indicating the powerful generalization of our predictor. Here, the predictor was interpreted by shapely additive explanation (SHAP) method which revealed several important substructures by mapping the featured fingerprints to molecular structures. Then, 15 new molecules were designed and predicted by our predictor to show superior IP than febuxostat. Finally, molecular docking simulation was performed to gain a deep insight into molecular binding mode with xanthine oxidase (XO) enzyme, showing that molecules with selenazole moiety, cyano group and isopropyl group tended to yield higher IP. The absorption, distribution, metabolism, excretion and toxicity (ADMET) prediction results further enhanced the potential of these novel XOIs as drug candidates. Overall, this work presents a QSAR model for accurate prediction of IP of XOIs, and is expected to provide new insights for further structure-guided design of novel XOIs.

The role of xanthine dioxygenase in the biosynthetic pathway of 2-aza-8-oxohypoxanthine of Lepista sordida

2-Azahypoxanthine (AHX) and 2-aza-8-oxohypoxanthine (AOH), discovered as causal substances of fairy rings are known to be endogenous in the fairy ring-forming Lepista sordida. In this study, we showed that xanthine dioxygenase, an a-ketoglutarate-dependent dioxygenase, might catalyze the conversion of AHX to AOH in the fungus. Furthermore, this enzyme is the first reported molybdopterin-independent protein of hypoxanthine metabolism.

A heterodimeric hyaluronate lyase secreted by the activated sludge bacterium Haliscomenobacter hydrossis

Haliscomenobacter hydrossis is a filamentous bacterium common in activated sludge. The bacterium was found to utilize hyaluronic acid, and hyaluronate lyase activity was detected in its culture. However, no hyaluronate lyase gene was found in the genome, suggesting the bacterium secretes a novel hyaluronate lyase. The purified enzyme exhibited two bands on SDS-PAGE and a single peak on gel filtration chromatography, suggesting a heterodimeric composition. N-terminal amino acid sequence and mass spectrometric analyses suggested that the subunits are molybdopterin-binding and [2Fe-2S]-binding subunits of a xanthine oxidase family protein. The presence of the cofactors was confirmed using spectrometric analysis. Oxidase activity was not detected, revealing that the enzyme is not an oxidase but a hyaluronate lyase. Nuclear magnetic resonance analysis of the enzymatic digest revealed that the enzyme breaks hyaluronic acid to 3-(4-deoxy-β-d-gluc-4-enuronosyl)-N-acetyl-d-glucosamine. As hyaluronate lyases (EC 4.2.2.1) are monomeric or trimeric, the enzyme is the first heterodimeric hyaluronate lyase.

Resonance Raman spectroscopy of pyranopterin molybdenum enzymes

Resonance Raman spectroscopy (rR) is a powerful spectroscopic probe that is widely used for studying the geometric and electronic structure of metalloproteins. In this focused review, we detail how resonance Raman spectroscopy has contributed to a greater understanding of electronic structure, geometric structure, and the reaction mechanisms of pyranopterin molybdenum enzymes. The review focuses on the enzymes sulfite oxidase (SO), dimethyl sulfoxide reductase (DMSOR), xanthine oxidase (XO), and carbon monoxide dehydrogenase. Specifically, we highlight how Mo-Ooxo, Mo-Ssulfido, Mo-Sdithiolene, and dithiolene CC vibrational modes, isotope and heavy atom perturbations, resonance enhancement, and associated Raman studies of small molecule analogs have provided detailed insight into the nature of these metalloenzyme active sites.

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.

Spectroscopic Studies of Mononuclear Molybdenum Enzyme Centers

A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of mononuclear molybdenum enzymes. Contributions to our understanding of the structure and function of each of the major families of these enzymes is considered, providing a perspective on how spectroscopy has impacted the field.

Is There a Connection between the Metabolism of Copper, Sulfur, and Molybdenum in Alzheimer’s Disease? New Insights on Disease Etiology

Alzheimer’s disease (AD) and other forms of dementia was ranked 3rd in both the Americas and Europe in 2019 in a World Health Organization (WHO) publication listing the leading causes of death and disability worldwide. Copper (Cu) imbalance has been reported in AD and increasing evidence suggests metal imbalance, including molybdenum (Mo), as a potential link with AD occurrence.We conducted an extensive literature review of the last 60 years of research on AD and its relationship with Cu, sulfur (S), and Mo at out of range levels.Weanalyzed the interactions among metallic elements’ metabolisms;Cu and Mo are biological antagonists, Mo is a sulfite oxidase and xanthine oxidase co-factor, and their low activities impair S metabolism and reduce uric acid, respectively. We found significant evidence in the literature of a new potential mechanism linking Cu imbalance to Mo and S abnormalities in AD etiology: under certain circumstances, the accumulation of Cu not bound to ceruloplasmin might affect the transport of Mo outside the blood vessels, causing a mild Mo deficiency that might lowerthe activity of Mo and S enzymes essential for neuronal activity. The current review provides an updated discussion of the plausible mechanisms combining Cu, S, and Mo alterations in AD.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, “general chemicals,” natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10–15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

U-shaped association of uric acid to overall-cause mortality and its impact on clinical management of hyperuricemia

Serum uric acid (SUA) is significantly elevated in obesity, gout, type 2 diabetes mellitus, and the metabolic syndrome and appears to contribute to the renal, cardiovascular and pulmonary comorbidities that are associated with these disorders. Most previous studies have focused on the pathophysiologic effects of high levels of uric acid (hyperuricemia). More recently, research has also shifted to the impact of hypouricemia, with multiple studies showing the potentially damaging effects that can be caused by abnormally low levels of SUA. Along with these observations, recent inconclusive data from human studies evaluating the treatment of hyperuricemia with xanthine oxidoreductase (XOR) inhibitors have added to the debate about the causal role of UA in human disease processes. SUA, which is largely derived from hepatic degradation of purines, appears to exert both systemic pro-inflammatory effects that contribute to disease and protective antioxidant properties. XOR, which catalyzes the terminal two steps of purine degradation, is the major source of both reactive oxygen species (O2^.-, H₂O₂) and UA. This review will summarize the evidence that both elevated and low SUA may be risk factors for renal, cardiovascular and pulmonary comorbidities. It will also discuss the mechanisms through which modulation of either XOR activity or SUA may contribute to vascular redox hemostasis. We will address future research studies to better account for the differential effects of high versus low SUA in the hope that this will identify new evidence-based approaches for the management of hyperuricemia.

Sulfide and transition metals - A partnership for life

Sulfide and transition metals often came together in Biology. The variety of possible structural combinations enabled living organisms to evolve an array of highly versatile metal-sulfide centers to fulfill different physiological roles. The ubiquitous iron‑sulfur centers, with their structural, redox, and functional diversity, are certainly the best-known partners, but other metal-sulfide centers, involving copper, nickel, molybdenum or tungsten, are equally crucial for Life. This review provides a concise overview of the exclusive sulfide properties as a metal ligand, with emphasis on the structural aspects and biosynthesis. Sulfide as catalyst and as a substrate is discussed. Different enzymes are considered, including xanthine oxidase, formate dehydrogenases, nitrogenases and carbon monoxide dehydrogenases. The sulfide effect on the activity and function of iron‑sulfur, heme and zinc proteins is also addressed.

Cotinine Hydroxylase CotA Initiates Biodegradation of Wastewater Micropollutant Cotinine in Nocardioides sp. Strain JQ2195

Cotinine is a stable toxic contaminant, produced as a by-product of smoking. It is of emerging concern due to its global distribution in aquatic environments. Microorganisms have the potential to degrade cotinine; however, the genetic mechanisms of this process are unknown. Nocardioides sp. strain JQ2195 is a pure-culture strain that has been reported to degrade cotinine at micropollutant concentrations. This strain utilizes cotinine as its sole carbon and nitrogen source. In this study, a 50-kb gene cluster (designated cot), involved in cotinine degradation, was predicted based on genomic and transcriptomic analyses. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3), which initiated cotinine catabolism, was identified and characterized. CotA from Shinella sp. strain HZN7 was heterologously expressed and purified and was shown to convert cotinine into 6-hydroxycotinine. H₂¹⁸O-labeling and electrospray ionization-mass spectrometry (ESI-MS) analysis confirmed that the hydroxyl group incorporated into 6-hydroxycotinine was derived from water. This study provides new molecular insights into the microbial metabolism of heterocyclic chemical pollutants. IMPORTANCE In the human body, cotinine is the major metabolite of nicotine, and 10 to 15% of generated cotinine is excreted in urine. Cotinine is a structural analogue of nicotine and is much more stable than nicotine. Increased tobacco consumption has led to high environmental concentrations of cotinine, which may have detrimental effects on aquatic ecosystems and human health. Nocardioides sp. strain JQ2195 is a unique cotinine-degrading bacterium. However, the underlying genetic and biochemical foundations of cotinine degradation are still unknown. In this study, a 50-kb gene cluster (designated cot) was identified by genomic and transcriptomic analyses as being involved in the degradation of cotinine. A novel three-component cotinine hydroxylase gene (designated cotA1A2A3) catalyzed cotinine to 6-hydroxy-cotinine. This study provides new molecular insights into the microbial degradation and enzymatic transformation of cotinine.

Water-Soluble α-Amino Acid Complexes of Molybdenum as Potential Antidotes for Cyanide Poisoning: Synthesis and Catalytic Studies of Threonine, Methionine, Serine, and Leucine Complexes

Water-soluble complexes are desirable for the aqueous detoxification of cyanide. Molybdenum complexes with α-amino acid and disulfide ligands with the formula K[(L)Mo₂O₂(μ-S)₂(S₂)] (L = leu (1), met (2), thr (3), and ser (4)) were synthesized in a reaction of [(DMF)₃MoO(μ-S)₂(S₂)] with deprotonated α-amino acids; leu, met, thr, and ser are the carboxylate anions of l-leucine, l-methionine, l-threonine, and l-serine, respectively. Potassium salts of α-amino acids (leu (1a), met (2a), thr (3a), and ser (4a)) were prepared as precursors for complexes 1-4, respectively, by employing a nonaqueous synthesis route. The ligand exchange reaction of [Mo₂O₂(μ-S)₂(DMF)₆](I)₂ with deprotonated α-amino acids afforded bis-α-amino acid complexes, [(L)₂Mo₂O₂(μ-S)₂] (6-8). A tris-α-amino acid complex, [(leu)₂Mo₂O₂(μ-S)₂(μ-leu + H)] (5; leu + H is the carboxylate anion of l-leucine with the amine protonated), formed in the reaction with leucine. 5 crystallized from methanol with a third weakly bonded leucine as a bridging bidentate carboxylate. An adduct of 8 with SCN^- coordinated, 9, crystallized and was structurally characterized. Complexes 1-4 are air stable and highly water-soluble chiral molecules. Cytotoxicity studies in the A549 cell line gave IC₅₀ values that range from 80 to 400 μM. Cyclic voltammetry traces of 1-8 show solvent-dependent irreversible electrochemical behavior. Complexes 1-4 demonstrated the ability to catalyze the reaction of thiosulfate and cyanide in vitro to exhaustively transform cyanide to thiocyanate in less than 1 h.

Molybdenum Enzymes and How They Support Virulence in Pathogenic Bacteria

Mononuclear molybdoenzymes are highly versatile catalysts that occur in organisms in all domains of life, where they mediate essential cellular functions such as energy generation and detoxification reactions. Molybdoenzymes are particularly abundant in bacteria, where over 50 distinct types of enzymes have been identified to date. In bacterial pathogens, all aspects of molybdoenzyme biology such as molybdate uptake, cofactor biosynthesis, and function of the enzymes themselves, have been shown to affect fitness in the host as well as virulence. Although current studies are mostly focused on a few key pathogens such as Escherichia coli, Salmonella enterica, Campylobacter jejuni, and Mycobacterium tuberculosis, some common themes for the function and adaptation of the molybdoenzymes to pathogen environmental niches are emerging. Firstly, for many of these enzymes, their role is in supporting bacterial energy generation; and the corresponding pathogen fitness and virulence defects appear to arise from a suboptimally poised metabolic network. Secondly, all substrates converted by virulence-relevant bacterial Mo enzymes belong to classes known to be generated in the host either during inflammation or as part of the host signaling network, with some enzyme groups showing adaptation to the increased conversion of such substrates. Lastly, a specific adaptation to bacterial in-host survival is an emerging link between the regulation of molybdoenzyme expression in bacterial pathogens and the presence of immune system-generated reactive oxygen species. The prevalence of molybdoenzymes in key bacterial pathogens including ESKAPE pathogens, paired with the mounting evidence of their central roles in bacterial fitness during infection, suggest that they could be important future drug targets.

Serum metabolic changes associated with dioxin exposure in a Chinese male cohort

Dioxins, a group of persistent organic pollutants, have been proved to correlate with ranges of diseases by activating the aryl hydrocarbon receptor (AhR). However, previous dioxin toxicity studies primarily focused on the activation of AhR with signaling pathways at gene and protein levels. The investigation of underlying mechanisms at the metabolic level is still necessary. In this study, serum samples of 48 and 47 healthy participants with the highest and lowest dioxin levels based on quartile distribution of the serum dioxin concentrations of 215 male adults were selected for metabolomics analysis by using liquid chromatography coupled with orbitrap high-resolution mass spectrometry to investigate dioxin-related metabolic responses. The identified potential biomarkers included acylcarnitines, fatty acids and derivatives, glycerophospholipids, etc. suggested that metabolic pathways such as fatty acid β-oxidation, essential fatty acid metabolism, arachidonic acid metabolism, glycerophospholipid and sphingolipid metabolism and purine metabolism were disturbed by dioxin exposure. The results indicated that people with high dioxin exposure levels were at the potential health risks of inflammation, liver and cardiovascular diseases. The metabolic findings may help understand the link between dioxin exposure and the diseases.

The O2-independent pathway of ubiquinone biosynthesis is essential for denitrification in Pseudomonas aeruginosa

Many proteobacteria, such as Escherichia coli, contain two main types of quinones: benzoquinones, represented by ubiquinone (UQ) and naphthoquinones, such as menaquinone (MK), and dimethyl-menaquinone (DMK). MK and DMK function predominantly in anaerobic respiratory chains, whereas UQ is the major electron carrier in the reduction of dioxygen. However, this division of labor is probably not very strict. Indeed, a pathway that produces UQ under anaerobic conditions in an UbiU-, UbiV-, and UbiT-dependent manner has been discovered recently in E. coli Its physiological relevance is not yet understood, because MK and DMK are also present in E. coli Here, we established that UQ9 is the major quinone of Pseudomonas aeruginosa and is required for growth under anaerobic respiration (i.e. denitrification). We demonstrate that the ORFs PA3911, PA3912, and PA3913, which are homologs of the E. coli ubiT, ubiV, and ubiU genes, respectively, are essential for UQ9 biosynthesis and, thus, for denitrification in P. aeruginosa These three genes here are called ubiTPa , ubiVPa , and ubiUPa We show that UbiVPa accommodates an iron-sulfur [4Fe-4S] cluster. Moreover, we report that UbiUPa and UbiTPa can bind UQ and that the isoprenoid tail of UQ is the structural determinant required for recognition by these two Ubi proteins. Since the denitrification metabolism of P. aeruginosa is believed to be important for the pathogenicity of this bacterium in individuals with cystic fibrosis, our results highlight that the O2-independent UQ biosynthetic pathway may represent a target for antibiotics development to manage P. aeruginosa infections.

Xanthine oxidoreductase inhibition – A review of computational aspect

Xanthine Oxidoreductase (XOR) exists in a variety of organisms from bacteria to humans and catalyzes the oxidation of hypoxanthine to xanthine and from xanthine to uric acid. Excessive uric acid could lead to gout and hyperuricemia. In this paper, we have reviewed the recent computational studies on xanthine oxidase inhibition. Computational methods, such as molecular dynamics (molecular mechanics), quantum mechanics, and quantum mechanics/molecular mechanics (QM/MM), have been employed to investigate the binding affinity of xanthine oxidase with synthesized and isolated nature inhibitors. The limitations of different computational methods for xanthine oxidase inhibition studies were also discussed. Implications of the computational approach could be used to help to understand the existing arguments on substrate/product orientation in xanthine oxidase inhibition, which allows designing new inhibitors with higher efficacy.

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.

Effects of Aster glehni Extract on Serum Uric Acid in Subjects with Mild Hyperuricemia: A Randomized, Placebo-Controlled Trial

Aster glehni extracts (AGE) reduced serum uric acid levels in hyperuricemia rats in several previous studies. However, its efficacy in human has not been yet explored. This study aimed at investigating the efficacy and safety of AGE on the anti-hyperuricemia effect in subjects with slightly high serum uric acid. A randomized, double-blinded, placebo-controlled clinical trial was conducted for 12 weeks. Eligible subjects were randomly assigned to either AGE (480 mg/day) or placebo. The primary endpoint was the change in serum uric acid concentrations from baseline to follow-up time points. The secondary endpoints were the change of serum xanthine oxidase activity, and the levels of C-reactive protein (CRP) and tumor necrosis factor alpha (TNF-α) in the blood from baseline to follow-up time points. Safety was assessed by clinical laboratory parameters and adverse events reported by subjects. Six weeks of AGE supplementation significantly reduced serum uric acid level from baseline (P = .0468) but at the end of the intervention the participants did not show the beneficial effect of AGE supplementation. Also, the serum uric acid level in the AGE group was not significantly different at the follow-up time points, when compared with placebo. The mean changes of secondary endpoints from baseline to each time point did not show significant differences within and between the two groups. There were no adverse events reported by subjects or changes in safety parameters after intervention. In conclusion, AGE supplementation for 12 weeks did not show significant benefits for reducing serum uric acid concentrations in subjects with mild hyperuricemia.

Cerebrospinal fluid-based metabolomics to characterize different types of brain tumors

BACKGROUND

Brain tumors cause significant morbidity and mortality due to rapid progression and high recurrence risks. Reliable biomarkers to improve diagnosis thereof are desirable.

OBJECTIVE

This work aimed to identify panels of biomarkers for diagnostic purposes using cerebrospinal fluid (CSF)-based metabolomics.

METHODS

A cohort of 163 histologically-proven patients with brain disorders was involved. Comprehensive CSF-based metabolomics was achieved by liquid chromatography-quadrupole time-of-flight spectrometric (LC-Q/TOF-MS) and multivariate statistical analyses. The diagnostic performance of the metabolic markers was evaluated using receiver operating characteristic curves.

RESULTS

A total of 508 ion features were detected by the LC-Q/TOF-MS analysis, of which 27 metabolites were selected as diagnostic markers to discriminate different brain tumor types. The area under the curve (AUC) was 0.91 for lung adenocarcinoma patients with brain metastases (MBT) vs. lung adenocarcinoma patients without brain metastases (NMBT), 0.83 for primary central nervous system lymphoma (PCNSL) vs. secondary central nervous system involvement of systemic lymphoma (SCNSL), 0.77 for PCNSL vs. MBT, 0.87 for SCNSL vs. MBT, 0.86 for MBT vs. nontumorous brain diseases (NT), and 0.80 for PCNSL vs. NT. Perturbed metabolic pathways between the comparisons related mainly to amino acids and citrate metabolism.

CONCLUSIONS

CSF-based metabolomics to a large extent reliably identifies significant metabolic differences between different brain tumors and shows great potential for diagnosis of brain tumors.

Ecological and Genomic Attributes of Novel Bacterial Taxa That Thrive in Subsurface Soil Horizons

While most bacterial and archaeal taxa living in surface soils remain undescribed, this problem is exacerbated in deeper soils, owing to the unique oligotrophic conditions found in the subsurface. Additionally, previous studies of soil microbiomes have focused almost exclusively on surface soils, even though the microbes living in deeper soils also play critical roles in a wide range of biogeochemical processes. We examined soils collected from 20 distinct profiles across the United States to characterize the bacterial and archaeal communities that live in subsurface soils and to determine whether there are consistent changes in soil microbial communities with depth across a wide range of soil and environmental conditions. We found that bacterial and archaeal diversity generally decreased with depth, as did the degree of similarity of microbial communities to those found in surface horizons. We observed five phyla that consistently increased in relative abundance with depth across our soil profiles: Chloroflexi, Nitrospirae, Euryarchaeota, and candidate phyla GAL15 and Dormibacteraeota (formerly AD3). Leveraging the unusually high abundance of Dormibacteraeota at depth, we assembled genomes representative of this candidate phylum and identified traits that are likely to be beneficial in low-nutrient environments, including the synthesis and storage of carbohydrates, the potential to use carbon monoxide (CO) as a supplemental energy source, and the ability to form spores. Together these attributes likely allow members of the candidate phylum Dormibacteraeota to flourish in deeper soils and provide insight into the survival and growth strategies employed by the microbes that thrive in oligotrophic soil environments.IMPORTANCE Soil profiles are rarely homogeneous. Resource availability and microbial abundances typically decrease with soil depth, but microbes found in deeper horizons are still important components of terrestrial ecosystems. By studying 20 soil profiles across the United States, we documented consistent changes in soil bacterial and archaeal communities with depth. Deeper soils harbored communities distinct from those of the more commonly studied surface horizons. Most notably, we found that the candidate phylum Dormibacteraeota (formerly AD3) was often dominant in subsurface soils, and we used genomes from uncultivated members of this group to identify why these taxa are able to thrive in such resource-limited environments. Simply digging deeper into soil can reveal a surprising number of novel microbes with unique adaptations to oligotrophic subsurface conditions.

Aldehyde oxidase and its role as a drug metabolizing enzyme

Aldehyde oxidase (AO) is a cytosolic enzyme that belongs to the family of structurally related molybdoflavoproteins like xanthine oxidase (XO). The enzyme is characterized by broad substrate specificity and marked species differences. It catalyzes the oxidation of aromatic and aliphatic aldehydes and various heteroaromatic rings as well as reduction of several functional groups. The references to AO and its role in metabolism date back to the 1950s, but the importance of this enzyme in the metabolism of drugs has emerged in the past fifteen years. Several reviews on the role of AO in drug metabolism have been published in the past decade indicative of the growing interest in the enzyme and its influence in drug metabolism. Here, we present a comprehensive monograph of AO as a drug metabolizing enzyme with emphasis on marketed drugs as well as other xenobiotics, as substrates and inhibitors. Although the number of drugs that are primarily metabolized by AO are few, the impact of AO on drug development has been extensive. We also discuss the effect of AO on the systemic exposure and clearance these clinical candidates. The review provides a comprehensive analysis of drug discovery compounds involving AO with the focus on developmental candidates that were reported in the past five years with regards to pharmacokinetics and toxicity. While there is only one known report of AO-mediated clinically relevant drug-drug interaction (DDI), a detailed description of inhibitors and inducers of AO known to date has been presented here and the potential risks associated with DDI. The increasing recognition of the importance of AO has led to significant progress in predicting the site of AO-mediated metabolism using computational methods. Additionally, marked species difference in expression of AO makes it is difficult to predict human clearance with high confidence. The progress made towards developing in vivo, in vitro and in silico approaches for predicting AO metabolism and estimating human clearance of compounds that are metabolized by AO have also been discussed.

Ubiquinone Biosynthesis over the Entire O2 Range: Characterization of a Conserved O2-Independent Pathway

In order to colonize environments with large O₂ gradients or fluctuating O₂ levels, bacteria have developed metabolic responses that remain incompletely understood. Such adaptations have been recently linked to antibiotic resistance, virulence, and the capacity to develop in complex ecosystems like the microbiota. Here, we identify a novel pathway for the biosynthesis of ubiquinone, a molecule with a key role in cellular bioenergetics. We link three uncharacterized genes of Escherichia coli to this pathway and show that the pathway functions independently from O₂. In contrast, the long-described pathway for ubiquinone biosynthesis requires O₂ as a substrate. In fact, we find that many proteobacteria are equipped with the O₂-dependent and O₂-independent pathways, supporting that they are able to synthesize ubiquinone over the entire O₂ range. Overall, we propose that the novel O₂-independent pathway is part of the metabolic plasticity developed by proteobacteria to face various environmental O₂ levels.

Most bacteria can generate ATP by respiratory metabolism, in which electrons are shuttled from reduced substrates to terminal electron acceptors, via quinone molecules like ubiquinone. Dioxygen (O₂) is the terminal electron acceptor of aerobic respiration and serves as a co-substrate in the biosynthesis of ubiquinone. Here, we characterize a novel, O₂-independent pathway for the biosynthesis of ubiquinone. This pathway relies on three proteins, UbiT (YhbT), UbiU (YhbU), and UbiV (YhbV). UbiT contains an SCP2 lipid-binding domain and is likely an accessory factor of the biosynthetic pathway, while UbiU and UbiV (UbiU-UbiV) are involved in hydroxylation reactions and represent a novel class of O₂-independent hydroxylases. We demonstrate that UbiU-UbiV form a heterodimer, wherein each protein binds a 4Fe-4S cluster via conserved cysteines that are essential for activity. The UbiT, -U, and -V proteins are found in alpha-, beta-, and gammaproteobacterial clades, including several human pathogens, supporting the widespread distribution of a previously unrecognized capacity to synthesize ubiquinone in the absence of O₂. Together, the O₂-dependent and O₂-independent ubiquinone biosynthesis pathways contribute to optimizing bacterial metabolism over the entire O₂ range.

Role of Molybdenum-Containing Enzymes in the Biotransformation of the Novel Ghrelin Receptor Inverse Agonist PF-5190457: A Reverse Translational Bed-to-Bench Approach

(R)-2-(2-methylimidazo[2,1-b]thiazol-6-yl)-1-(2-(5-(6-methylpyrimidin-4-yl)-2,3-dihydro-1H-inden-1-yl)-2,7-diazaspiro[3.5]nonan-7-yl)ethan-1-one (PF-5190457) was identified as a potent and selective inverse agonist of the ghrelin receptor [growth hormone secretagogue receptor 1a (GHS-R1a)]. The present translational bed-to-bench work characterizes the biotransformation of this compound in vivo and then further explores in vitro metabolism in fractions of human liver and primary hepatocytes. Following oral administration of PF-5190457 in a phase 1b clinical study, hydroxyl metabolites of the compound were observed, including one that had not been observed in previously performed human liver microsomal incubations. PF-6870961 was biosynthesized using liver cytosol, and the site of hydroxylation was shown to be on the pyrimidine using nuclear magnetic resonance spectroscopy. The aldehyde oxidase (AO) inhibitor raloxifene and the xanthine oxidase inhibitor febuxostat inhibited the formation of PF-6870961 in human liver cytosol, suggesting both enzymes were involved in the metabolism of the drug. However, greater inhibition was observed with raloxifene, indicating AO is a dominant enzyme in the biotransformation. The intrinsic clearance of the drug in human liver cytosol was estimated to be 0.002 ml/min per milligram protein. This study provides important novel information at three levels: 1) it provides additional new information on the recently developed novel compound PF-5190457, the first GHS-R1a blocker that has moved to development in humans; 2) it provides an example of a reverse translational approach where a discovery in humans was brought back, validated, and further investigated at the bench level; and 3) it demonstrates the importance of considering the molybdenum-containing oxidases during the development of new drug entities. SIGNIFICANCE STATEMENT: PF-5190457 is a novel ghrelin receptor inverse agonist that is currently undergoing clinical development for treatment of alcohol use disorder. PF-6870961, a major hydroxyl metabolite of the compound, was observed in human plasma, but was absent in human liver microsomal incubations. PF-6870961 was biosynthesized using liver cytosol, and the site of hydroxylation on the pyrimidine ring was characterized. Inhibitors of aldehyde oxidase and xanthine oxidase inhibited the formation of PF-6870961 in human liver cytosol, suggesting both enzymes were involved in the metabolism of the drug. This information is important for patient selection in subsequent clinical studies.

Anaerobic C-H Oxyfunctionalization: Coupling of Nitrate Reduction and Quinoline Hydroxylation in Recombinant Pseudomonas putida

Whole-cell biocatalysis for C-H oxyfunctionalization depends on and is often limited by O₂ mass transfer. In contrast to oxygenases, molybdenum hydroxylases use water instead of O₂ as an oxygen donor and thus have the potential to relieve O₂ mass transfer limitations. Molybdenum hydroxylases may even allow anaerobic oxyfunctionalization when coupled to anaerobic respiration. To evaluate this option, the coupling of quinoline hydroxylation to denitrification is tested under anaerobic conditions employing Pseudomonas putida (P. putida) 86, capable of aerobic growth on quinoline. P. putida 86 reduces both nitrate and nitrite, but at low rates, which does not enable significant growth and quinoline hydroxylation. Introduction of the nitrate reductase from Pseudomonas aeruginosa enables considerable specific quinoline hydroxylation activity (6.9 U g_CDW ^-1 ) under anaerobic conditions with nitrate as an electron acceptor and 2-hydroxyquinoline as the sole product (further metabolization depends on O₂ ). Hydroxylation-derived electrons are efficiently directed to nitrate, accounting for 38% of the respiratory activity. This study shows that molybdenum hydroxylase-based whole-cell biocatalysts enable completely anaerobic carbon oxyfunctionalization when coupled to alternative respiration schemes such as nitrate respiration.

Antioxidant, antiapoptotic, antigenotoxic, and hepatic ameliorative effects of L-carnitine and selenium on cadmium-induced hepatotoxicity and alterations in liver cell structure in male mice

L-carnitine (LC) and selenium (Se) have significant protective and antioxidant effects on several tissues. Cadmium (Cd), widely used in some industries and emitted from fossil fuels, is a heavy metal having a number of side effects, including hepatotoxicity. This study aims to assess the ameliorative function of both LC and SeCl₄ on cadmium chloride (CdCl₂)-induced liver toxicity. In total, 70 male mice included in this study were allocated to seven groups: control, CdCl₂, LC, SeCl₄, CdCl₂ plus SeCl₄, CdCl₂ plus LC, CdCl₂ plus SeCl₄ and LC groups. Hepatic aminotransferase (aspartate aminotransferase [AST] and alanine transaminase [ALT]) activity and tumor necrosis factor-alpha [TNF-α] levels, as well as the antioxidant biomarkers (superoxide dismutase [SOD], glutathione reductase [GRx], glutathione-S-transferase [GST] and catalase [CAT], were examined. Histological and transmission electron microscopic [TEM] variations in the liver were used as indicators of liver damage after the administration of CdCl₂-alone or CdCl₂ with LC, SeCl₄, or both. Genotoxic effects of CdCl₂ were also evaluated and the possible roles of SeCl₄ and/or LC on the expression of the antioxidant enzymes were studied. Results showed that administration of LC and SeCl₄ decreased CdCl₂-induced increase in ALT and AST levels and reduced oxidative stress to normal levels. In addition, LC combined with SeCl₄ had a highly synergistic effect and elevated significantly the enzymatic antioxidants and decreased lipid peroxidation levels compared with those in the CdCl₂-treated group. It is clear from the data that both LC and SeCl₄ inhibit liver injury and improve the redox state in mice.

LC/MS-Based Polar Metabolite Profiling Identified Unique Biomarker Signatures for Cervical Cancer and Cervical Intraepithelial Neoplasia Using Global and Targeted Metabolomics

Cervical cancer remains one of the most prevalent cancers among females worldwide. Therefore, it is important to discover new biomarkers for early diagnosis of cervical intraepithelial neoplasia (CIN) and cervical cancer, preferably non-invasive ones. In the present study, we aimed to identify unique metabolic signatures for CINs and cervical cancers using global and targeted metabolomic profiling. Plasma samples (69 normal, 55 CIN1, 42 CIN2/3, and 60 cervical cancer) were examined by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-QTOF-MS) coupled with multivariate statistical analysis. Metabolic pathways were analyzed using the integrated web-based tool MetaboAnalyst. A multivariate logistic regression analysis was conducted to evaluate the combined association of metabolites and human papillomavirus (HPV) status with the risk of cervical carcinogenesis. A total of 28 metabolites exhibiting discriminating levels among normal, CIN, and cervical cancer patients (Kruskal–Wallis test p < 0.05) were identified in the global profiling analysis. The pathway analysis showed significantly altered alanine, aspartate, and glutamate metabolic pathways (FDR p-value < 0.05) in both the discovery and validation phases. Seven metabolites (AMP, aspartate, glutamate, hypoxanthine, lactate, proline, and pyroglutamate) were discriminated between CINs and cervical cancer versus normal (area under the curve (AUC) value > 0.8). The levels of these metabolites were significantly high in patients versus normal (p < 0.0001) and were associated with increased risk of developing CIN2/3 and cervical cancer. Additionally, elevated levels of the seven metabolites combined with positive HPV status were correlated with substantial risk of cancer progression. These results demonstrated that metabolomics profiling is capable of distinguishing CINs and cervical cancers from normal and highlighted potential biomarkers for the early detection of cervical carcinogenesis.

Modified Chuanhu anti-gout mixture, a traditional Chinese medicine, protects against potassium oxonate-induced hyperuricemia and renal dysfunction in mice

Objective

Acute gout is a painful, inflammatory arthritis that features a rapidly escalating inflammatory response resulting from the formation of monosodium urate crystals in the affected joint space. Previously, we found that Chuanhu anti-gout mixture (CAGM) had similar effects as colchicine against gout in the clinic. Subsequently, to improve its effectiveness and efficacy, we modified the original formulation of CAGM. The current study evaluated the effectiveness of the modified formulation in mice.

Methods

Potassium oxonate (PO) was used to establish a mouse model of hyperuricemia. Plasma levels of uric acid and creatine were determined using the respective test kits. Hepatic xanthine oxidase (XOD) expression was examined by enzyme-linked immunosorbent assay. To explore the underlying mechanism, renal urate transporter 1 (URAT1) mRNA levels were evaluated by quantitative real-time PCR. Allopurinol and benzbromarone were used as reference drugs.

Results

The original CAGM and its modified high-dose formulation significantly reduced serum uric acid and creatine levels in hyperuricemic mice. In addition, the CAGM-treated groups displayed lower mRNA levels of hepatic XOD and renal URAT1.

Conclusions

CAGM and its modified formulation significantly ameliorated PO-induced hyperuricemia in mice, which might be partially attributable to reductions of hepatic XOD and renal URAT1 levels.

Carbon Monoxide Dehydrogenases

Carbon monoxide dehydrogenases (CODHs) catalyze the reversible oxidation of CO with water to CO₂, two electrons, and two protons. Two classes of CODHs exist, having evolved from different scaffolds featuring active sites built from different transition metals. The basic properties of both classes are described in this overview chapter.

Putting xanthine oxidoreductase and aldehyde oxidase on the NO metabolism map: Nitrite reduction by molybdoenzymes

Nitric oxide radical (NO) is a signaling molecule involved in several physiological and pathological processes and a new nitrate-nitrite-NO pathway has emerged as a physiological alternative to the "classic" pathway of NO formation from L-arginine. Since the late 1990s, it has become clear that nitrite can be reduced back to NO under hypoxic/anoxic conditions and exert a significant cytoprotective action in vivo under challenging conditions. To reduce nitrite to NO, mammalian cells can use different metalloproteins that are present in cells to perform other functions, including several heme proteins and molybdoenzymes, comprising what we denominated as the "non-dedicated nitrite reductases". Herein, we will review the current knowledge on two of those "non-dedicated nitrite reductases", the molybdoenzymes xanthine oxidoreductase and aldehyde oxidase, discussing the in vitro and in vivo studies to provide the current picture of the role of these enzymes on the NO metabolism in humans.

Study of aldehyde oxidase by micellar electrokinetic chromatography separation of O6 -benzylguanine and 8-oxo-O6 -benzylguanine

A separation method for O⁶ -benzylguanine (O⁶ -BG) and 8-oxo-O⁶ -benzylguanine (8-oxo-O⁶ -BG) is developed by using MEKC. This study includes the optimization of separation and incubation parameters for both off-line and on-line procedures. The BGE consisted of 25 mM sodium phosphate buffer-methanol (70:30, v/v), apparent pH 7.4, in which SDS and methyl-β-cyclodextrin were dissolved yielding final concentrations of 50 and 15 mM, respectively. Separations were performed at 15 kV using an untreated fused-silica capillary (40 cm length, effective length is 30 cm) with the detection wavelength at 195 nm. The capillary was kept at 15°C. Good performances were demonstrated for the repeatability and linearity. The LOQ was determined to be 14 μM for 8-oxo-O⁶ -BG (S/N = 10). The accuracy values showed a bias of +7.9% for 50 μM and -7.0% for 100 μM. Premix and transverse diffusion of laminar flow profiles (TDLFP) methods were used for on-line mixing and reaction of the substrate O⁶ -BG with aldehyde oxidase. Both procedures were successful in mixing as well as subsequent separation of the substrate and the metabolite, while the repeatability of TDLFP (14.7% (n = 3)) was much better than the premix technique.

Mixed-valence dimolybdenum complexes containing hard oxo and soft carbonyl ligands: synthesis, structure, and electrochemistry of Mo2(O)(CO)2(μ-κ2-S(CH2)nS)2(κ2-diphosphine)

Mixed-valence dimolybdenum complexes Mo2(O)(CO)2{μ-κ2-S(CH2)nS}2(κ2-Ph2P(CH2)mPPh2) (n = 2, 3; m = 1, 2) (1-4) have been synthesized from one-pot reactions of fac-Mo(CO)3(NCMe)3 and dithiols, HS(CH2)nSH, in the presence of diphosphines. The dimolybdenum framework is supported by two thiolate bridges, with one molybdenum carrying a terminal oxo ligand and the second two carbonyls. The dppm (m = 1) products exist as a pair of diastereomers differing in the relative orientation of the two carbonyls (cis and trans) at the Mo(CO)2(dppm) center, while dppe (m = 2) complexes are found solely as the trans isomers. Small amounts of Mo(CO){κ3-S(CH2CH2S)2}(κ2-dppe) (5) also result from the reaction using HS(CH2)2SH and dppe. The bonding in isomers of 1-4 has been computationally explored by DFT calculations, trans diastereomers being computed to be more stable than the corresponding pair of cis diastereomers for all. The calculations confirm the existence of Mo[triple bond, length as m-dash]O and Mo-Mo bond orders and suggest that the new dimeric compounds are best viewed as Mo(v)-Mo(i) mixed-valence systems. The electrochemical properties of 1 have been investigated by CV and show a reversible one-electron reduction associated with the Mo(v) centre, while two closely spaced irreversible oxidation waves are tentatively assigned to oxidation of the Mo(i) centre of the two isomers as supported by DFT calculations.

S-allyl cysteine as potent anti-gout drug: Insight into the xanthine oxidase inhibition and anti-inflammatory activity

S-allyl cysteine (SAC) is known for its various beneficial effects such as neuroprotection and immunomodulation. The beneficial effect of SAC against gout has not been explored. The present study aims to describe the two roles of SAC: (1) inhibitory effect against xanthine oxidase (XO) enzyme activity; and (2) anti-inflammatory property against MSU crystal-induced gouty inflammation in rat. The inhibitory effect of SAC against bovine XO enzyme activity was determined in vitro. In silico analysis was carried out to determine the intermolecular interaction between SAC and bovine XO. MSU crystal was injected in the right paw of the rat to induce gouty inflammation. SAC (40 mg/kg body weight) and colchicine (positive control; 1 mg/kg body weight) was given for 3 days. At the end of the treatment, the oxidative stress, antioxidant parameters and mitochondrial function were determined in the ankle joint tissue. The concentration of inflammatory cytokines such as TNF-α and IL-1β was measured in the serum using ELISA. SAC inhibited (IC₅₀ value, 33 μg/ml) XO enzyme activity in a competitive mode with corresponding Ki value of 4 μg/ml. In silico analysis predicted the interaction of SAC with the amino acids such as Arg880, Phe798, Phe914 and Phe1009 of XO enzyme. The root mean square deviation, root mean square fluctuation and free energy calculation values confirmed the stable SAC-XO interaction. The inhibition of SAC on XO enzyme activity in in vivo was further confirmed by silkworm model. SAC through reducing oxidative stress, enhancing antioxidants, protecting mitochondrial function has shown anti-inflammatory effect against MSU crystal-induced gout which was observed as reduced level of inflammatory markers in the serum. The medicinal potential of SAC as a preventive agent through its XO inhibitory property as well as curative agent through its anti-inflammatory property against gout has been understood from the present study.

A eukaryotic nicotinate-inducible gene cluster: convergent evolution in fungi and bacteria

Nicotinate degradation has hitherto been elucidated only in bacteria. In the ascomycete Aspergillus nidulans, six loci, hxnS/AN9178 encoding the molybdenum cofactor-containing nicotinate hydroxylase, AN11197 encoding a Cys2/His2 zinc finger regulator HxnR, together with AN11196/hxnZ, AN11188/hxnY, AN11189/hxnP and AN9177/hxnT, are clustered and stringently co-induced by a nicotinate derivative and subject to nitrogen metabolite repression mediated by the GATA factor AreA. These genes are strictly co-regulated by HxnR. Within the hxnR gene, constitutive mutations map in two discrete regions. Aspergillus nidulans is capable of using nicotinate and its oxidation products 6-hydroxynicotinic acid and 2,5-dihydroxypyridine as sole nitrogen sources in an HxnR-dependent way. HxnS is highly similar to HxA, the canonical xanthine dehydrogenase (XDH), and has originated by gene duplication, preceding the origin of the Pezizomycotina. This cluster is conserved with some variations throughout the Aspergillaceae. Our results imply that a fungal pathway has arisen independently from bacterial ones. Significantly, the neo-functionalization of XDH into nicotinate hydroxylase has occurred independently from analogous events in bacteria. This work describes for the first time a gene cluster involved in nicotinate catabolism in a eukaryote and has relevance for the formation and evolution of co-regulated primary metabolic gene clusters and the microbial degradation of N-heterocyclic compounds.

Predicting ovarian cancer recurrence by plasma metabolic profiles before and after surgery

BACKGROUND

Previous metabolomic studies have revealed that plasma metabolic signatures may predict epithelial ovarian cancer (EOC) recurrence. However, few studies have performed metabolic profiling of pre- and post-operative specimens to investigate EOC prognostic biomarkers.

OBJECTIVE

The aims of our study were to compare the predictive performance of pre- and post-operative specimens and to create a better model for recurrence by combining biomarkers from both metabolic signatures.

METHODS

Thirty-five paired plasma samples were collected from 35 EOC patients before and after surgery. The patients were followed-up until December, 2016 to obtain recurrence information. Metabolomics using rapid resolution liquid chromatography-mass spectrometry was performed to identify metabolic signatures related to EOC recurrence. The support vector machine model was employed to predict EOC recurrence using identified biomarkers.

RESULTS

Global metabolomic profiles distinguished recurrent from non-recurrent EOC using both pre- and post-operative plasma. Ten common significant biomarkers, hydroxyphenyllactic acid, uric acid, creatinine, lysine, 3-(3,5-diiodo-4-hydroxyphenyl) lactate, phosphohydroxypyruvic acid, carnitine, coproporphyrinogen, L-beta-aspartyl-L-glutamic acid and 24,25-hydroxyvitamin D3, were identified as predictive biomarkers for EOC recurrence. The area under the receiver operating characteristic (AUC) values in pre- and post-operative plasma were 0.815 and 0.909, respectively; the AUC value after combining the two sets reached 0.964.

CONCLUSION

Plasma metabolomic analysis could be used to predict EOC recurrence. While post-operative biomarkers have a predictive advantage over pre-operative biomarkers, combining pre- and post-operative biomarkers showed the best predictive performance and has great potential for predicting recurrent EOC.

Global and targeted serum metabolic profiling of colorectal cancer progression

BACKGROUND

Patients with colorectal adenoma polyps (PLPs) are at higher risk for developing colorectal cancer (CRC). However, the development of improved and robust biomarkers to enable the screening, surveillance, and early detection of PLPs and CRC continues to be a challenge. The aim of this study was to identify biomarkers of progression to CRC through metabolomic profiling of human serum samples with a multistage approach.

METHODS

Metabolomic profiling was conducted with the Metabolon platform for 30 CRC patients, 30 PLP patients, and 30 control subjects, and this was followed by the targeted validation of the top metabolites in an additional set of 50 CRC patients, 50 PLP patients, and 50 controls with liquid chromatography-tandem mass spectrometry. Unconditional multivariate logistic regression models, adjusted for covariates, were used to evaluate associations with PLP and CRC risk.

RESULTS

For the discovery phase, 404 serum metabolites were detected, with 50 metabolites showing differential levels between CRC patients, PLP patients, and controls (P for trend < .05). After validation, the 3 top metabolites (xanthine, hypoxanthine, and d-mannose) were validated: lower levels of xanthine and hypoxanthine and higher levels of d-mannose were found in PLP and CRC cases versus controls. A further exploratory analysis of metabolic pathways revealed key roles for the urea cycle and caffeine metabolism associated with PLP and CRC risk. In addition, a joint effect of the top metabolites with smoking and a significant interaction with the body mass index were observed. An analysis of the ratio of hypoxanthine levels to xanthine levels indicated an association with CRC progression.

CONCLUSIONS

These results suggest the potential utility of circulating metabolites as novel biomarkers for the early detection of CRC. Cancer 2017;123:4066-74. © 2017 American Cancer Society.

Studies on the aerobic utilization of synthesis gas (syngas) by wild type and recombinant strains of Ralstonia eutropha H16

The biotechnical platform strain Ralstonia eutropha H16 was genetically engineered to express a cox subcluster of the carboxydotrophic Oligotropha carboxidovoransOM5, including (i) the structural genes coxM, -S and -L, coding for an aerobic carbon monoxide dehydrogenase (CODH) and (ii) the genes coxD, -E, -F and -G, essential for the maturation of CODH. The cox_Oc genes expressed under control of the CO₂ -inducible promoter P_L enabled R. eutropha to oxidize CO to CO₂ for the use as carbon source, as demonstrated by ¹³ CO experiments, but the recombinant strains remained dependent on H₂ as external energy supply. Therefore, a synthetic metabolism, which could be described as 'carboxyhydrogenotrophic', was established in R. eutropha. With this extension of the bacterium's substrate range, growth in CO-, H₂ - and CO₂ -containing artificial synthesis gas atmosphere was enhanced, and poly(3-hydroxybutyrate) synthesis was increased by more than 20%.

Vanadium(V) complexes with hydrazides and their spectroscopic and biological properties

The present study explores the synthesis and inhibitory potential of vanadium(V) complexes of hydrazides (1c-12c) against oxidative enzymes including xanthine oxidase and lipoxygenase (LOX). In addition, non-enzymatic radical scavenging activities of these complexes were also determined. On the basis of spectral, elemental and physical data, synthesized vanadium(V) complexes are tentatively assigned to have an octahedral geometry with two hydrazide ligands and two oxo groups forming a negatively charged sphere complex with ammonium as counter ion. This is further verified by the conductivity studies of the complexes. Results show that hydrazide ligands (1-12) and their respective vanadium(V) complexes (1c-12c) posses scavenging and inhibition potential against DPPH and LOX, respectively. However, contrary to that uncoordinated ligands showed no activity against nitric oxide, superoxide and xanthine oxidase whereas their complexes showed varying degree of activity. These studies indicate that geometry of complex, nature and position of substituent groups play a vital role in scavenging and inhibition potential of these compounds.