2e1q
From Proteopedia
Crystal Structure of Human Xanthine Oxidoreductase mutant, Glu803Val
Structural highlights
DiseaseXDH_HUMAN Defects in XDH are the cause of xanthinuria type 1 (XU1) [MIM:278300. Xanthinuria is characterized by excretion of very large amounts of xanthine in the urine and a tendency to form xanthine stones. Uric acid is strikingly diminished in serum and urine. XU1 is due to isolated xanthine dehydrogenase. XU1 patients can metabolize allopurinol.[1] [2] [3] [4] FunctionXDH_HUMAN Key enzyme in purine degradation. Catalyzes the oxidation of hypoxanthine to xanthine. Catalyzes the oxidation of xanthine to uric acid. Contributes to the generation of reactive oxygen species. Has also low oxidase activity towards aldehydes (in vitro).[5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedXanthine oxidase (oxidoreductase; XOR) and aldehyde oxidase (AO) are similar in protein structure and prosthetic group composition, but differ in substrate preference. Here we show that mutation of two amino acid residues in the active site of human XOR for purine substrates results in conversion of the substrate preference to AO type. Human XOR and its Glu803-to-valine (E803V) and Arg881-to-methionine (R881M) mutants were expressed in an Escherichia coli system. The E803V mutation almost completely abrogated the activity towards hypoxanthine as a substrate, but very weak activity towards xanthine remained. On the other hand, the R881M mutant lacked activity towards xanthine, but retained slight activity towards hypoxanthine. Both mutants, however, exhibited significant aldehyde oxidase activity. The crystal structure of E803V mutant of human XOR was determined at 2.6 A resolution. The overall molybdopterin domain structure of this mutant closely resembles that of bovine milk XOR; amino acid residues in the active centre pocket are situated at very similar positions and in similar orientations, except that Glu803 was replaced by valine, indicating that the decrease in activity towards purine substrate is not due to large conformational change in the mutant enzyme. Unlike wild-type XOR, the mutants were not subject to time-dependent inhibition by allopurinol. Human xanthine oxidase changes its substrate specificity to aldehyde oxidase type upon mutation of amino acid residues in the active site: roles of active site residues in binding and activation of purine substrate.,Yamaguchi Y, Matsumura T, Ichida K, Okamoto K, Nishino T J Biochem. 2007 Apr;141(4):513-24. Epub 2007 Feb 14. PMID:17301077[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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