Pyridine coenzyme analogues. Synthesis and characterization of .alpha.- and .beta.-nicotinamide arabinoside adenine dinucleotides

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Abstract
The synthesis and characterization of a new pyridine coenzyme analogue containing a nicotinamide arabinonucleotide moiety are reported. The redox potentials are -339 mV for .beta.-oxidized nicotinamide arabinoside adenine dinucleotide and -319 mV for .alpha.-oxidized nicotinamide adenine dinucleotide, and the .lambda.max is 346 and 338 nm for .beta.- and .alpha.-reduced nicotinamide arabinoside adenine dinucleotides (araNADH), respectively. Anomerization of the reduced analogues leads to a 5:1 ratio of .alpha.-araNADH to .beta.-araNADH at 90.degree. C. These results establish that the relative configuration of the 2''-hydroxyl to the base is the primary determinant for the configuration-dependent changes in .lambda.max, the redox potential of the pyridine nucleotides, and the preferred anomeric configuration of the reduced coenzymes. Comparison of the 1H and 31P NMR spectral data of the analogues with those for the ribo coenzymes is reported and the conformational analysis discussed. The coenzyme properties of the arabino analogues have been evaluated with yeast and horse liver alcohol dehydrogenases. Both the .alpha.- and .beta.-anomers are found to serve as coenzymes, and the stereochemistry of hydride transfer is identical for both anomers.