Human nicotinamide N-methyltransferase gene: molecular cloning, structural characterization and chromosomal localization.

Genomic DNA clones for nicotinamide N-methyltransferase (NNMT), an enzyme that catalyzes drug and xenobiotic metabolism, were isolated from a human chromosome 11-specific DNA library. Study of one of those clones, when combined with PCR-based experiments performed with human genomic DNA, made it possible to determine the structure of the human NNMT gene. The gene was approximately 16.5 kb in length and consisted of 3 exons and 2 introns. Transcription initiation for the NNMT gene occurred 105-109 nucleotides 5'-upstream from the cDNA translation initiation codon on the basis of the results of both primer extension and 5'-rapid amplification of cDNA ends. NNMT mapped to chromosome band 11q23.1 by fluorescence in situ hybridization.