Molecular cloning, chromosomal localization, tissue mRNA levels, bacterialexpression, and enzymatic properties of human NMN adenylyltransferase

A 1329-base pair clone isolated from a human placenta cDNA library contains a full-length 837-base pair coding region for a 31.9-kDa protein whose ded uced primary structure exhibits high homology to consensus sequences found in other NMN adenylyltransferases. Northern blotting detected a major 3.1-k ilobase mRNA transcript as well as a minor 4.1-kilobase transcript in all h uman tissues examined. In several cancer cell lines, lower levels of mRNA e xpression were clearly evident. The gene encoding the human enzyme was mapp ed to chromosome band 1p32-35. High efficiency bacterial expression yielded 1.5 mg of recombinant enzyme/liter of culture medium. The molecular and ki netic properties of recombinant human NMR adenylyltransferase provide new d irections for investigating metabolic pathways involving this enzyme.