XDH

XDH Full Name

xanthine dehydrogenase

XDH Introduction

Xanthine Dehydrogenase (XDH) is a key molybdenum-containing enzyme involved in the terminal steps of purine degradation, catalyzing the sequential oxidation of hypoxanthine to xanthine and xanthine to uric acid. It belongs to the xanthine oxidoreductase family and exists in two interconvertible forms: xanthine dehydrogenase (XDH) and xanthine oxidase (XO). This conversion is a critical biochemical feature of the enzyme and can occur through reversible sulfhydryl oxidation or irreversible proteolysis. Recent mechanistic studies have demonstrated that the transition from XDH to XO is associated with disulfide bond formation at specific cysteine residues, particularly Cys-535 and Cys-995, and may proceed in a substrate- and oxygen-dependent autocatalytic manner. This redox-dependent interconversion significantly alters the enzyme's catalytic properties and determines its role in cellular metabolism.

Functionally, XDH plays a central role in maintaining purine homeostasis and regulating intracellular redox balance. In its dehydrogenase form, XDH preferentially transfers electrons to NAD+, contributing to controlled metabolic flux and limiting oxidative damage. Upon conversion to XO, the enzyme instead utilizes molecular oxygen as an electron acceptor, producing reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide. This functional shift links XDH activity to oxidative stress, inflammation, and immune signaling pathways. In addition to its role in mammalian systems, XDH has been extensively studied in plants, where it participates in purine catabolism, nitrogen recycling, and stress responses. By regulating metabolites such as allantoin and allantoate, plant XDH contributes to reactive oxygen species scavenging and enhances tolerance to environmental stresses including drought, salinity, and high temperature.

Aberrant XDH activity and its conversion to XO are closely associated with multiple pathological conditions. Increased enzymatic activity contributes to hyperuricemia and gout through excessive uric acid production, while elevated ROS generation from the XO form is implicated in endothelial dysfunction, cardiovascular diseases, and ischemia–reperfusion injury. In cancer, altered XDH expression and redox imbalance have been linked to tumor progression and metabolic reprogramming. Furthermore, XDH has emerged as a promising therapeutic target, as small molecules and natural compounds such as isorhamnetin have been shown to interact with its active site and inhibit enzymatic activity. These findings support the development of XDH-targeted strategies for regulating purine metabolism, reducing oxidative stress, and treating related metabolic and inflammatory diseases.

Alternate Names for XDH

XDH; xanthine dehydrogenase; XO; XOR; xanthine dehydrogenase/oxidase; xanthine oxidoreductase;

• 1.Kusano T, et al.; The mechanism and significance of the conversion of xanthine dehydrogenase to xanthine oxidase in mammalian secretory gland cells. Redox Biol. 2023, 59:102573.
  2.Dissanayake LV, et al.; Lack of xanthine dehydrogenase leads to a remarkable renal decline in a novel hypouricemic rat model. iScience. 2022, 25(9):104887.