Table 1.

The major human NAT2 alleles and their associated phenotype^a.

Allele	Nucleotide change b							Phenotype
	G191A	C282T	T341C	C481T	G590A	A803G	G857A
NAT2*4								rapid
NAT2*5A			x	x				slow
NAT2*5B			x	x		x		slow
NAT2*5C			x			x		slow
NAT2*6A		x			x			slow
NAT2*6B					x			slow
NAT2*7A							x	slow
NAT2*7B		x					x	slow
NAT2*12A						x		rapid
NAT2*12B		x				x		rapid
NAT2*13		x						rapid
NAT2*14A	x							slow
NAT2*14B	x	x						slow

Nucleotide substitutions shown in bold have a functional consequence on enzyme activity. Bold-faced alleles contain functional polymorphisms and are hence associated with the slow acetylator phenotype. Classification of NAT2 alleles into different clusters is based on the most functionally significant nucleotide substitution present: the NAT2*5, NAT2*6, NAT2*7 and NAT2*14 clusters possess signature nucleotide substitutions at positions 341, 590, 857 and 191, respectively and are hence all decreased function alleles ('slow alleles'). The others display enzymatic activity comparable to the rapid acetylator allele NAT2*4. There are significant interethnic differences in NAT2 allele distribution and frequency [14, 15].

^a Adapted from Hein et al. [3]. NAT2 nomenclature is accessible on the internet at website http://www.louisville.edu/medschool/pharmacology/NAT.html

^b Only changes from the reference sequence (NAT2*4) are indicated.