AOX1

Last update 08 May 2025

Basic Info

Synonyms

Aldehyde oxidase, aldehyde oxidase 1, AO

+ [3]

Introduction

Oxidase with broad substrate specificity, oxidizing aromatic azaheterocycles, such as N1-methylnicotinamide, N-methylphthalazinium and phthalazine, as well as aldehydes, such as benzaldehyde, retinal, pyridoxal, and vanillin. Plays a key role in the metabolism of xenobiotics and drugs containing aromatic azaheterocyclic substituents. Participates in the bioactivation of prodrugs such as famciclovir, catalyzing the oxidation step from 6-deoxypenciclovir to penciclovir, which is a potent antiviral agent. Is probably involved in the regulation of reactive oxygen species homeostasis. May be a prominent source of superoxide generation via the one-electron reduction of molecular oxygen. May also catalyze nitric oxide (NO) production via the reduction of nitrite to NO with NADH or aldehyde as electron donor. May play a role in adipogenesis.

100 Clinical Results associated with AOX1

100 Translational Medicine associated with AOX1

0 Patents (Medical) associated with AOX1

2,604

Literatures (Medical) associated with AOX1

01 May 2025·Free Radical Biology and Medicine

HepG2 cells do not express xanthine oxidoreductase (XOR): Implications for XOR and uric acid-related research

Article

Author: King, Rachel D ; Chen, I-Tzu ; Giromini, Andrew G ; Kelley, Eric E ; Khoo, Nicholas K H ; Chapa, Matthew G

Although the relative extent of xanthine oxidoreductase (XOR) varies considerably in human tissues, the greatest specific activity is reported in the liver and intestines. Unlike murine models, where primary hepatocytes are readily available, human counterparts are not. As such, investigators often utilize the human carcinoma cell line HepG2 for in vitro experimentation as these cells proliferate well in culture medium. Some of the studies using HepG2 cells for proof-of-principal experimentation focus on uric acid (UA) and/or XOR activity. However, it has been reported that hepatocellular carcinoma diminishes XOR expression to nearly unmeasurable levels when compared to normal cell counterparts which posits the question of validity in the context of using HepG2 cells for XOR/UA assessments. As such, we closely examined XOR expression, protein abundance, and enzymatic activity in HepG2 cells and compared these results to an immortalized murine hepatocyte line (AML12) as well as murine liver homogenate. We report the absence of detectable XOR message, protein, and enzymatic activity in HepG2 cells. Since cellular XOR expression has been reported to be stimulated by hypoxia and serum starvation, we then exposed both AML12 and HepG2 cells to hypoxia (1% O₂) for 24 h or serum starvation which impacted XOR activity in AML12 cells, but not in HepG2 cells. Knowing that several studies report XOR activity in HepG2 cells, we compared a commonly used non-selective XOR assay kit to our sensitive and selective HPLC/electrochemical assay. The kit assay indicated XOR activity in HepG2 cells; however, XOR inhibition did not diminish this activity. To account for alternative enzymatic oxidization of hypo/xanthine to UA, we investigated HepG2 cells for aldehyde oxidase (AO) abundance and found immunodetectable AO protein as well as AO-inhibitable conversion of hypoxanthine to UA; albeit, at a much slower rate when compared to XOR. In toto, these data confirm that HepG2 cells do not demonstrate XOR activity and thus commonly used kit assays for XOR, in the absence of XOR inhibitor controls, may indicate a positive response induced by an alternative source of peroxide and UA such as AO.

01 May 2025·Molecular Genetics and Metabolism

Early postnatal hepatocyte transplantation in a child with molybdenum cofactor deficiency type B

Article

Author: Lemonde, H ; Dhawan, A ; Fitzpatrick, E ; Bansal, S ; Selvanathan, A ; Schwahn, B C ; White, F J ; Turner, C ; Kankananarachchi, I ; Fairbanks, L

Molybdenum cofactor deficiencies (MoCD) are a group of inborn errors of metabolism that result in impaired synthesis of molybdenum cofactor, crucial for the function of three oxidases (sulfite oxidase, xanthine oxidase and aldehyde oxidase). Most patients present with severe neonatal-onset epileptic encephalopathy, hypotonia, poor feeding and apnoea, with death typically occurring within the first three years of life. Whilst there is now an emerging therapy for MoCD Type A (cPMP/fosdenopterin), this treatment is not effective for MoCD Type B and there is no treatment for isolated sulfite oxidase deficiency (ISOD). Liver directed gene delivery is a potential alternative therapy for sulfite intoxication disorders. We report an attempt to use hepatocyte transplantation as a treatment option for MoCD Type B, in an infant with a strong family history of neonatal-onset disease and early mortality. Six transfusions of hepatocytes were given between Day 1 and Day 18 of life, totalling around 1 × 10⁹ cells with immunosuppressive cover. Concomitantly dietary protein restriction was maintained at 2 g/kg, including 0.7 g/kg of methionine- and cyst(e)ine-free amino acid mixture. The aim was to utilize hepatocyte transplantation as a bridge to liver transplantation. Whilst there was evidence of biochemical stabilization with reduction in concentrations of sulfite and S-sulfocysteine and a moderate increase in urate levels compared to the sibling, the treatment was not able to prevent acute brain injury from sulfite toxicity which was evident in neuroimaging at 35 h of age. This correlated clinically with ongoing seizures as well as minimal developmental progress.

09 Apr 2025·Journal of Experimental Botany

Useful or merely convenient: can enzymatic antioxidant activity be used as a proxy for abiotic stress tolerance?

Review

Author: Xu, Le ; Mittler, Ron ; Shabala, Sergey ; Liu, Huaqiong

AbstractDuring their lifespan, plants are often exposed to a broad range of stresses that change their redox balance and lead to accumulation of reactive oxygen species (ROS). The traditional view is that this comes with negative consequences to cells structural integrity and metabolism and, to prevent this, plants evolved a complex and well-coordinated antioxidant defence system that relies on the operation of a range of enzymatic and non-enzymatic antioxidants (AO). Due to the simplicity of measuring their activity, and in light of the persistent dogma that stress-induced ROS accumulation is detrimental for plants, it is not surprising that enzymatic AOs have often been advocated as suitable proxies for stress tolerance as well as potential targets for improving tolerance traits. However, there are a growing number of reports showing either no changes or even down-regulation of AO systems in stressed plants. Moreover, ROS are recognized now as important second messengers operating in both local and systemic signalling, synergistically interacting with the primary stressor, to regulate gene expression needed for optimal acclimatization. This work critically assesses the suitability of using enzymatic AOs as a proxy for stress tolerance or as a target for crop genetic improvement. It is concluded that constitutively higher AO activity may interfere with stress-induced ROS signalling and be a disadvantage for plant stress tolerance.

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AOX1

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