Structure/Function Evaluations of Single Nucleotide Polymorphisms in Human N-Acetyltransferase 2

Abstract

Arylamine N-acetyltransferase 2 (NAT2) modifies drug efficacy/toxicity and cancer risk due to its role in bioactivation and detoxification of arylamine and hydrazine drugs and carcinogens. Human NAT2 alleles possess a combination of single nucleotide polymorphisms (SNPs) associated with slow acetylation phenotypes. Clinical and molecular epidemiology studies investigating associations of NAT2 genotype with drug efficacy/toxicity and/or cancer risk are compromised by incomplete and sometimes conflicting information regarding genotype/phenotype relationships. Studies in our laboratory and others have characterized the functional effects of SNPs alone, and in combinations present in alleles or haplotypes. We extrapolate this data generated following recombinant expression in yeast and COS-1 cells to assist in the interpretation of NAT2 structure. Whereas previous structural studies used homology models based on templates of N-acetyltransferase enzyme crystal structures from various prokaryotic species, alignment scores between bacterial and mammalian N-acetyltransferase protein sequences are low (~ 30%) with important differences between the bacterial and mammalian protein structures. Recently, the crystal structure of human NAT2 was released from the Protein Data Bank under accession number 2PFR. We utilized the NAT2 crystal structure to evaluate the functional effects of SNPs resulting in the protein substitutions R64Q (G191A), R64W (C190T), I114T (T341C), D122N (G364A), L137F (A411T), Q145P (A434C), E167K (G499A), R197Q (C590A), K268R (A803G), K282T (A845C), and G286E (G857A) of NAT2. This analysis advances understanding of NAT2 structure-function relationships, important for interpreting the role of NAT2 genetic polymorphisms in bioactivation and detoxification of arylamine and hydrazine drugs and carcinogens.

Safety, Tolerability, and Pharmacokinetics of Etamicastat, a Novel Dopamine-β-Hydroxylase Inhibitor, in a Rising Multiple-Dose Study in Young Healthy Subjects

“…Human NAT1 and NAT2 loci are highly polymorphic, with more than 25 alleles identified in each locus. [28,29] Within this polymorphic population, different phenotypes have been identified for both forms, NAT1 and NAT2. As an important metabolizing en- zyme in humans, the polymorphism of human NAT expression, especially NAT2, raises concerns about drug-drug interactions during clinical use.…”

N-Acetyltransferase 2: ultra-slow acetylators enter the stage

“…Persons with an impaired NAT2 capacity-so-called slow acetylatorshave two slow copies of the gene, whereas the presence of one or two rapid or wild-type copies of the gene leads to an intermediate or rapid genotype-so-called rapid acetylators. The relationship between genotype and NAT2 activity has been investigated extensively in vitro using bacterial, yeast and eukaryotic cell systems (Selinski et al 2014;Walraven et al 2008;García-Closas et al 2011). Furthermore, the caffeine test (using a further NAT2 substrate) allows the determination of the metabolic capacity Sabbagh et al 2011).…”

Association between N-acetyltransferase 2 polymorphisms and pancreatic cancer risk: a meta-analysis

“…Both suggested that the publication bias had little influence on the results of this meta-analysis. Study subject numbers are listed by the rate of acetylation associated with their different N-acetyltransferase 2 genotypes (Walraven et al, 2008). Table 1.…”

“…NAT2 is a polymorphic gene located on chromosome 8p21.3-23.1 that encodes a 290-amino acid protein (Blum et al, 1990). The NAT2 polymorphism has been classified into three phenotypes based on the allelic variant: fast (rapid), intermediate, and slow (Walraven et al, 2008). The alteration of the NAT2 acetylator status caused by the polymorphism might decrease its enzymatic activity and lead to the absence of efficient detoxification, further elevating cancer risk (Wikman et al, 2001;Cui et al, 2011).…”