We have recently found that nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent agonist that triggers Ca2+ release from intracellular stores of sea urchin egg homogenates, and that its action is distinct from effect of IP, and cADPR (J. Biol. Chem. 270:3216, 1995). Synthesis of NAADP by exchange of nicotinamide (NiAm) for nicotinic acid (NiAc) catalyzed by the NAD(P)-glycohydrolase was previously described. We now explored whether ADP-ribosyl cyclase, an enzyme which catalyzes synthesis of cADPR from NAD but does not contain NAD(P) glycohydrolase activity can catalyze also NAADP synthesis by transglycosidation with NiAc. Incubation of purified Aplysia californica ovotestes ADP-ribosyl cyclase with NADP resulted in synthesis of NAADP when NiAc was added into the mixture. Further, cADPR synthesis from NAD by Aplysia ADP-ribosyl-cyclase was inhibited by NiAc in concentrations needed for synthesis of NAADP. Extracts from sea urchin egg homogenates and from HL-60 cells which catalyze synthesis of cADPR from NAD also catalyzed synthesis of NAADP when incubated with 5 mM NiAc and 0.5 mM NADP. Furthermore, the cADPR synthesis from NAD was inhibited by addition of NiAc. Both the synthesis of cADPR and NAADP in HL-60 cells was inhibited by 10 mM DTT. Conversely, neither synthesis of cADPR nor NAADP by Aplysia enzyme was inhibited by DTT. We conclude that ADP-ribosyl cyclase from different sources catalyzes not only cyclization of NAD to cADPR, but also synthesis of NAADP from NADP by transglycosidation with NiAc.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology