Conformations of Diphosphopyridine Coenzymes upon Binding to Dehydrogenases

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Abstract
The binding of oxidized as well as reduced coenzyme to some dehydrogenases has been studied under different concentration ratios and temperatures by nuclear magnetic resonance spectroscopy. A significant difference in the spectral behavior between DPN(+) and DPNH upon binding is interpreted in terms of fast and slow on-off rates relative to the nuclear magnetic resonance time scale in the binding of these two coenzymes. Significant downfield shifts of DPN(+) were observed upon binding, comparable in magnitude to those expected upon opening (destacking) of the coenzymes in the case of chicken-muscle and lobster-tail lactate dehydrogenase (EC 1.1.1.27) and yeast alchol dehydrogenase (EC 1.1.1.1.). A preliminary survey of several other dehydrogenases is consistent with these findings. In the case of 3-phosphoglyceraldehyde dehydrogenase, there is a possibility that the coenzyme exists in the folded form.