Ribose, lactate dehydrogenase coenzyme

Specific nucleotide recognition in the ternary complex between the enzyme lactate dehydrogenase and the modified coenzyme NAD+-pyruvate (NAD = nicotinamide-adenine-dinucleotide). NAD+ consists of two nucleotides, adenosine-5 -phosphate and nicotinamide ribose-5 -phosphate, which are linked through a pyrophosphate bond. 

High-resolution H n.m.r. spectroscopy has been used to probe the conformations of a number of o-ribofuranosylamine derivatives and such rigid molecules as 2,2 -cyclonucleosides and nucleoside 3, 5 -phosphates in aqueous solution. H N.m.r. spectroscopy has also been used to study details of the intramolecular association and conformations of a- and j8-linked pyridine ribo-nucleosides and their 5 -phosphates. The results were analysed in terms of base-D-ribose, o-ribose-side-chain, and base-side-chain interactions and the conformational restraints imposed by the cis HO-2-HO-3 interaction in jS-nucleo-tides and the additional cis HO-2 -base interaction in a-nucleotides. H N.m.r. measurements - including measurements of nuclear Overhauser effects and paramagnetic relaxations effected by Mn + cations - have been used to investigate the preferred conformation about the jV-glycosidic bond of 8-amino-, 8-methyl-amino-, and 8-dimethylamino-adenylic acid, all of which competitively inhibit the coenzyme NADH in the reaction with chicken-muscle lactate dehydrogenase. The primary and secondary amines were shown to prefer anti conformations, whereas the tertiary amine prefers a syn conformation. 

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