Chemoenzymatic Synthesis of Analogues of the Second Messenger Candidate Cyclic Adenosine 5'-Diphosphate Ribose
A broad substrate specificity for adenosine 5'-diphosphate ribosyl cyclase is demonstrated by cyclisation of ribose- and purine-modified nicotinamide adenine dinucleotide analogues to mimics of cyclic adenosine 5'-diphosphate ribose, generating a straightforward route for structural modification of this important Ca2+ -mobilising nucleotide.
Ashamu, Gloria A.,Galione, Antony,Potter, Barry V. L.
Cyclic ADP-ribose: Synthesis and structural assignment
Cyclic ADP-ribose (cADPR) is a naturally occurring cyclic nucleotide and a potent mediator of calcium mobilization in many mammalian tissues. Previous studies have shown that cADPR is synthesized from β-NAD+ via the scission of the nicotinamide-ribose linkage and cyclization by forming a new bond between the ribose and the nitrogen of the adenine ring. However, the position and stereochemistry of this newly formed linkage were not unequivocally determined. In this study we have established that cADPR has the anomeric carbon of the ribose attached onto the N1-nitrogen of the adenine nucleus via a β-N-glycosyl linkage. The structural assignment was made by correlating cADPR to N1-(5'-phosphoribosyl)AMP, a known intermediate of histidine biosynthesis. This was achieved by cleaving the pyrophosphate bond of cADPR under conditions (DMSO/tert-butoxide) not perturbing the integrity of the C-N glycosyl bond. Furthermore, cADPR was successfully synthesized by cyclization of N1-(5'-phosphoribosyl)ATP catalyzed by NAD+ pyrophosphorylase in an organic solvent-aqueous medium.
cADPR Analogues: Effect of an Adenosine 2′- Or 3′-Methoxy Group on Conformation
(Matrix presented) The 2′-OMe-A (2) and 3′-OMe-A (3) analogues of the calcium release agent cADPR (1) were prepared and their solution structures studied by NMR spectroscopy. Compared to 1, 2 shows a shift in its A ring conformation and changes in its R ring N:S and γt: γ+ ratios, while 3 displays a significant change in the conformation of its A ring γ-bond.
Graham, Steven M.,Macaya, Daniel J.,Sengupta, Raghuvir N.,Turner, Kevin B.