PARTICIPATION OF NICOTINAMIDE MONONUCLEOTIDE IN PYRIDINE NUCLEOTIDE SYNTHESIS IN TUMOR AND HOST LIVER

Evidence is presented to show that nicotinamide-7- 14 C in low or high doses is incorporated into nicotinamide mononucleotide (NMN) by Ehrlich ascites cells and host liver in vivo. Nicotinamide mononucleotide formed from nicotinamide-7- 14 C has been isolated from incubations of Sephadex-treated extracts of ascites cell acetone powders with 5-phosphoribosyl-1-pyrophosphate and characterized by spectral and chemical analysis. The apparent K m and V max for NMN synthesis from nicotinamide have been determined. NMN- 14 C has been shown to form NAD- 14 C in the same extracts in the presence of ATP, and the apparent V max and K m of this process have been determined. The role of NMN in NAD synthesis is discussed.