title: Functional characterization of human xanthine oxidase allelic variants.
abstract: OBJECTIVE
  Xanthine oxidase (XO) catalyzes the oxidation of endogenous and exogenous purines and pyrimidines. In this study, we speculated that individual variations in XO activity are caused by genetic variations in the XO gene.
  
  
  METHODS
  To investigate the genetic variations in XO in 96 Japanese participants, denaturing high-performance liquid chromatography was used. To assess the effects of these variations on enzymatic activity, wild-type XO and 21 types of variant XO--including those in the database and those just discovered--were transiently expressed in COS-7 cells.
  
  
  RESULTS
  Three nonsynonymous single nucleotide polymorphisms, including 514G>A (Gly172Arg), 3326A>C (Asp1109Thr), and 3662A>G (His1221Arg) were identified in Japanese participants. Functional characterization of 21 XO variants showed a deficiency in enzyme activity in two variants (Arg149Cys and Thr910Lys); low activity (intrinsic clearance, CLint: 22-69% compared with the wild-type) in six variants (Pro555Ser, Arg607Gln, Thr623Ile, Asn909Lys, Pro1150Arg, and Cys1318Tyr); and high activity (CLint: approximately two-fold higher than that in the wild-type) in two variants (Ile703Val and His1221Arg).
  
  
  CONCLUSIONS
  These results suggest that several single nucleotide polymorphisms in the XO gene are involved in individual variations in XO activity. In addition, such findings will be useful to identify xanthinuria patients.
authors.affiliation: Department of Clinical Pharmacotherapeutics, Tohoku Pharmaceutical University, Sendai, Japan.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Kudo
authors.forename: Toshiko
authors.initials: T
authors.lastname: Moteki
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Sasaki
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Konno
authors.forename: Shuta
authors.initials: S
authors.lastname: Ujiie
authors.forename: Akemi
authors.initials: A
authors.lastname: Onose
authors.forename: Michinao
authors.initials: M
authors.lastname: Mizugaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiratsuka
mesh_terms: D000483:Alleles; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D007564:Japan; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010597:Pharmacogenetics; D020641:Polymorphism, Single Nucleotide; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019820:Xanthine / Q000652:urine; D014969:Xanthine Oxidase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D019820:Xanthine; D014969:Xanthine Oxidase