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Journal of Bacteriology, July 2005, p. 4521-4530, Vol. 187, No. 13
0021-9193/05/$08.00+0 doi:10.1128/JB.187.13.4521-4530.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Ulfar Bergthorsson,
Yaping Xu,
Jared Sterneckert,
Behzad Khodaverdian, and
John R. Roth*
Department of Biology, University of Utah, Salt Lake City, Utah 84112
Received 12 January 2005/ Accepted 28 March 2005
Salmonella enterica can obtain pyridine from exogenous nicotinamide mononucleotide (NMN) by three routes. In route 1, nicotinamide is removed from NMN in the periplasm and enters the cell as the free base. In route 2, described here, phosphate is removed from NMN in the periplasm by acid phosphatase (AphA), and the produced nicotinamide ribonucleoside (NmR) enters the cell via the PnuC transporter. Internal NmR is then converted back to NMN by the NmR kinase activity of NadR. Route 3 is seen only in pnuC* transporter mutants, which import NMN intact and can therefore grow on lower levels of NMN. Internal NMN produced by either route 2 or route 3 is deamidated to nicotinic acid mononucleotide and converted to NAD by the biosynthetic enzymes NadD and NadE.
Present address: Biochemistry Department, University of Utah Medical School, Salt Lake City, UT 84112.
Present address: Biology Department, University of New Mexico, Albuquerque, NM 87131-0001.
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