Diphosphopyridine nucleotide reactions with

According to investigations by Theorell 54), the oxidation of alcohol by alcohol dehydrogenase from liver involves a binary complex of dehydrogenase -h diphosphopyridine nucleotide (DPN), while with yeast dehydrogenase the complex is ternary and includes the alcohol. Vennesland and Westheimer 55) have established, using deuteroethanol with yeast alcohol dehydrogenase, that the reaction is... 

It would be well to point out a few examples which illustrate the overlap of asymmetric reduction studies and molecular biochemistry. Diphosphopyridine nucleotide (DPN) and triphospho-pyridine nucleotide (TPN) are important coenzymes in biochemical oxidation reduction reactions. Certain enzymes function as catalysts for the reversible transfer of hydrogen between these nucleotides and a substrate for which the enzyme is specific. For example, DPN and the enzyme, alcohol dehydrogenase (ADH), form a redox system with ethanol. Using deuterium labeled reducing agent and substrate, Westheimer, Vennesland,... 

It is likely that the hydrogen from XH2 dissociates into a hydride ion H (= H+ + 2 e ) and a proton, H+. The oxidized diphosphopyridine nucleotide then combines with the hydride ion leaving the proton in solution as hydrogen ion. These reactions can be summarized as follows ... 

With our sensitive spectrophotometric methods (11,12,17) we have shown how the reaction velocity constants for peroxidase action can be measured directly from the kinetics of formation and disappearance of the enzyme-substrate complex. This is perhaps the most elegant and incisive method of assay and can now be successfully applied not only to hemo-proteins but also to diphosphopyridine nucleotide enzymes. The detaUs of the methods lie outside the scope of this review and are available in detail elsewhere (3,6). 

The mechanism of synthesis of flavin adenine dinucleotide was established by Schrecker and Komberg 1S6) with a purified enzyme from brewer s yeast. The coenzyme is formed by a reaction analogous to the synthesis of diphosphopyridine nucleotide (1S7). 

Geraci, G. Gibson, Q. H. (1967). The reaction of liver dehydrogenase with reduced diphosphopyridine nucleotide. Journal of Biological Chemistry, 242, 4275-8. 

In similar circumstances l-(2,6-dichlorobenzyl)pyridinium bromide is said to give a salt (88), which can be oxidized to the methide (89). Several such reactions are known Closely related are those of diphosphopyridine nucleotide with carbonyl compounds in alkali 35 ... 

Diphosphopyridine nucleotide and analogous quaternary pyridinium salts form complexes with bisulphite and with thiols 2-5, xhe orientation of these additions is usually uncertain and may vary with the reaction solvent used " 4, The dithionite addition products formed by quaternary pyridinium salts have attracted interest because of their connection with the dithionite reduction of diphosphopyridine nucleotide (p. 259). Thus, the formation of a 1,4-dihydropyridine (122) by reduction of (120) has been represented 6 as proceeding through a 1,2-addition product (121). Regardless of the correctness or otherwise of structure (121), the relevance of the intermediate for diphosphopyridine nucleotide reduction by dithionite has been questioned, and the yellow intermediate formed in this reaction has been formulated 8 as a charge-transfer complex between the pyridinium nucleus and 820 (see p. 261). 

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