Correlation between acetylator phenotypes and genotypes of polymorphic arylamine N-acetyltransferase in human liver

Southern blot analysis was performed with genomic DNAs from 86 human subjects using the 32P-labeled cDNA for polymorphic arylamine N-acetyltransferase (EC 2.3.1.5) in human liver recently cloned in our laboratory. Three types of N-acetyltransferase gene were identified. Gene 1 contains a 5.5-kilobase (kb) KpnI fragment with a BamHI site; gene 2 contains a 5.5-kb KpnI fragment without a BamHI site; and gene 3 contains a 5.0-kb KpnI fragment with a BamHI site. The combination of these three genes generated five genotypes. Acetylator phenotypes were determined in 29 healthy volunteers by isoniazid loading tests, and they were classified as rapid (10 subjects), intermediate (16 subjects), or slow (3 subjects) acetylators. Rapid acetylators were homozygotes of gene 1. Intermediate acetylators were heterozygotes of either genes 1 and 2 or genes 1 and 3. There were two exceptional cases who were classified as intermediate acetylators but were homozygotes of gene 1. Slow acetylators were either heterozygote of genes 2 and 3 or homozygotes of gene 3. These results indicate that gene 1 corresponds to high N-acetyltransferase activity, while gene 2 and gene 3 give rise to low N-acetyltransferase activity.