User:Josie N. Harmon/Sandbox 1
From Proteopedia
Xanthine Oxidase in Complex with 6-Mercaptopurine
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Xanthine oxidase is characterized as a molybdenum containing enzyme that catalyzes the hydroxylation of a sp2 hybrized carbon in a broad range of aromatic heterocycles and aldehydes. The crystal structure of the bovine xanthine oxidase complex contains two active sites with varying intrinsic activity. In eukaryotes xanthine oxidases exist as homodimers with each monomer containing four redox-active sites. The crystalline structure of a xanthine oxidase offers a better view of the , the ferredoxin iron sulfur, ,clusters, and .
6-Mercaptopurine is metabolized hepatically by xanthine oxidase. Xanthine oxidase is considered a component of xanthine oxidoreductase, which is an enzyme known to generate reactive oxygen species. This enzyme is considered to be extremely important in the catabolism of purines.
6-Mercaptopurine is classified as a cytotoxic chemotherapy agent frequently used to treat acute lymphoblastic leukemia (ALL), non-Hodgkin's lymphoma, psoriatic arthritis, and inflammatory bowel disease. The drug belongs to a class of compounds referred to as purine antagonists that inhhibits DNA and RNA synthesis. The drug acts as a antimetabolite and incorporates itself into DNA or RNA and virtually inhibits the growth of cancer cells. The drug allopurinol, which is used to treat gout, is very similar in structure to 6-mercaptopurine and it is this similarity that makes the use of the two drugs simultaneously contraindicated. Allopurinol acts by inhibiting xanthine oxidase, the enzyme that metabolizes 6-mercaptopurine.
A of the structure is represented with purple arrows representing the alpha helix structures and gold arrows representing the beta strand structures. The of the protein backbone can also be noted by the blue arrows on the structure. The helix consists of various protein residues and an between two aromatic residues is shown here, with the blue structure representing phenylalanine and the green structure representing tryptophan
