Functional characterization of single-nucleotide polymorphisms and haplotypes of human N-acetyltransferase 2.
Human N-acetyltransferase 2 (NAT2) is polymorphic in humans and may associate with cancer risk by modifying individual susceptibility to cancers from carcinogen exposure. Since molecular epidemiological studies investigating these associations usually include determining NAT2 single-nucleotide polymorphisms (SNPs), haplotypes or genotypes, their conclusions can be compromised by the uncertainty of genotype-phenotype relationships. We characterized NAT2 SNPs and haplotypes by cloning and expressing recombinant NAT2 allozymes in mammalian cells. The reference and variant recombinant NAT2 allozymes were characterized for arylamine N-acetylation and O-acetylation of N-hydroxy-arylamines. SNPs and haplotypes that conferred reduced enzymatic activity did so by reducing NAT2 protein without changing NAT2 mRNA levels. Among SNPs that reduced catalytic activity, G191A (R64Q), G590A (R197Q) and G857A (G286E) reduced protein half-life but T341C (I114T), G499A (E167K) and A411T (L137F) did not. G857A (G286E) and the major haplotype possessing this SNP (NAT2 7B) altered the affinity to both substrate and cofactor acetyl coenzyme A, resulting in reduced catalytic activity toward some substrates but not others. Our results suggest that coding region SNPs confer slow acetylator phenotype by multiple mechanisms that also may vary with arylamine exposures.
Zang
Yu
Y
Department of Pharmacology and Toxicology, James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Doll
Mark A
MA
Zhao
Shuang
S
States
J Christopher
JC
Hein
David W
DW
D000107:Acetylation; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D019556:COS Cells; D002522:Chlorocebus aethiops; D006239:Haplotypes; D006801:Humans; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D013418:Sulfamethazine / Q000037:antagonists & inhibitors / Q000378:metabolism
D013418:Sulfamethazine; D001191:Arylamine N-Acetyltransferase; C478900:NAT2 protein, human