Functional characterization of human xanthine oxidase allelic variants.
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.
Kudo
Mutsumi
M
Department of Clinical Pharmacotherapeutics, Tohoku Pharmaceutical University, Sendai, Japan.
Moteki
Toshiko
T
Sasaki
Takamitsu
T
Konno
Yumiko
Y
Ujiie
Shuta
S
Onose
Akemi
A
Mizugaki
Michinao
M
Ishikawa
Masaaki
M
Hiratsuka
Masahiro
M
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*
D017931:DNA Primers; D011994:Recombinant Proteins; D019820:Xanthine; D014969:Xanthine Oxidase