DEHYDROGENASE-REDUCED COENZYME DIFFERENCE SPECTRA, THEIR RESOLUTION AND RELATIONSHIP TO STEREOSPECIFICITY OF HYDROGEN TRANSFER

The binding of reduced diphosphopyridine nucleotide to any specific dehydrogenase causes changes in the ultraviolet absorption spectrum of the reduced coenzyme. The 340-mμ regions of the resulting difference spectra can all be resolved into two simple operations on a reduced diphosphopyridine nucleotide spectrum; a shift of the band itself to a higher or lower wavelength without any change in shape and a uniform hyper- or hypochromicity of that peak. We find that A stereospecific dehydrogenases produce blue shifts while B stereospecific dehydrogenases produce red shifts (with the possible exception of mitochondrial malate dehydrogenase). The size of most of the shifts observed here is sufficiently large that the concentration of reduced diphosphopyridine nucleotide involved can be calculated. We have previously shown that changes in conformation of reduced diphosphopyridine nucleotide produce difference spectra resolvable into various combinations of the same components. Most of the shifts of the coenzyme spectrum in dehydrogenase complexes, however, are far too large to be accounted for by a simple opening or closing of the reduced diphosphopyridine nucleotide molecule. © 1969, American Chemical Society. All rights reserved.