FIG. 3.

Synthesis of NAD through the NaMN intermediate. (A) In the Preiss-Handler pathway, nicotinic acid is salvaged to NAD via NaMN and NaAD intermediates. The pathway is depicted with S. cerevisiae gene names over the arrows and E. coli gene names under the arrows. (B) In F. tularensis, the de novo pathway depicted in Fig. 2A was found, but the nadD gene was found to be missing. Utilization of NaMN depends on NaMN amidation to NMN by a unique nadE gene, followed by NMN adenylylation by nadM.