Nicotinamide deuterium labeled

As another example, studies with deuterium-labeled substrates have shown that the reaction of ethanol with the coenzyme nicotinamide adenine dinucleotide (NAD+) catalyzed by yeast alcohol dehydrogenase occurs with exclusive removal of the pro-R hydrogen from ethanol and with addition only to the Re face of NAD" ". 

PROBLEM 15.12 The mechanism of enzymatic oxidation has been studied by isotopic labeling with the aid of deuterated derivatives of ethanol. Specify the number of deuterium atoms that you would expect to find attached to the dihydropyridine ring of the reduced form of the nicotinamide adenine dinucleotide coenzyme following enzymatic oxidation of each of the alcohols given ... 

Asymmetric reduction of carbonyl compounds and production of isotopically labelled species has been achieved. A system based on deuterated formate and formate dehydrogenase provides the best system for the introduction of deuterium through nicotinamide-cofactor catalysed process (Table 2). 

Theoretical calculations of charge distribution on the nicotinamide ring by B. Pullman in Paris agree with a hydride attack at position C-4. Experimental evidence comes from reaction with a deuterated alcohol and isolation of the pyridinium salt. Methylation and oxidation take place without loss of deuterium, proving that the labeling occurs only at C-4. 

The de terated coenzyme, DPND, formed from DPN and MeCD20H in the presence of enzyme, transfers all its deuterium to Me.GHO on enzymatic reoxidation, whereas DPND formed from D2O and dithionite transfers only half of its deuterium in this process the enzymatic reduction is stereospecific but the dithionite reduction is not 3. Quaternization and Decker oxidation of nicotinamide obtained from DPND, formed by both enzymatic and dithionite reduction of DPN, gave 3-carboxamido-l-methyl-2- and -6-pyridone, both of which were still labelled (the enzymatic product half as much as the dithionite product). Thus, the quaternary nicotinamide nucleus of DPN is converted into the 1,4-dihydro form both by enzymatic and dithionite reductioni084 xhe same point was also proved for various quaternary derivatives of nicotinamide and for DPN by observing that the product of dithionite/D20 reduction could enzymatically transfer deuterium to an acceptor, whilst quaternary salts synthesized with deuterium at C(2) or G(6), and then reduced with dithionite/H20, could notions. 

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