Copyright © 1997, American Society for Microbiology Characterization of Nicotinamide Mononucleotide

The enzyme nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) catalyzes the synthesis of NAD1 and nicotinic acid adenine dinucleotide. It has been purified to homogeneity from cellular extracts of the thermophilic archaeon Sulfolobus solfataricus. Through a database search, a highly significant match was found between its N-terminal sequence and a hypothetical protein coded by the thermophilic archaeon Methanococcus jannaschii MJ0541 open reading frame (GenBank accession no. U67503). The MJ0541 gene was isolated, cloned into a T7-based vector, and expressed in Escherichia coli cells, yielding a high level of thermophilic NMN adenylyltransferase activity. The expressed protein was purified to homogeneity by a single-step chromatographic procedure. Both the subunit molecular mass and the N-terminal sequence of the pure recombinant protein were as expected from the deduced amino acid sequence of the MJ0541 open reading frame-encoded protein. Molecular and kinetic properties of the enzymes from both archaea are reported and compared with those already known for the mesophilic eukaryotic NMN adenylyltransferase. NAD1 synthesis can be accomplished either via de novo pathways or through preformed pyridine ring salvage routes (13). All such pathways converge to the reaction nicotinamide mononucleotide (NMN) (or nicotinic acid mononucleotide)