Triphosphopyridine Nucleotide Diaphorase from Wheat Germ.

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Abstract
A TPNH-specific diaphorase has been purified approximately 10-fold from wheat germ. The enzyme is associated with a DPNH-specific diaphorase, but the relative activities of the 2 enzymes vary so widely in different protein fractions that they are considered to be separate systems. There appears to be no requirement for added flavin or metal ions. Metal binding agents have no effect on enzyme activity. The addition of a heat-stable organic factor obtained from a crude extract of wheat germ results in a 7- to 10-fold increase in cytochrome c reductase and oxidase activities of the enzyme. Several quinone-like compounds also served to transform the diaphorase to a cytochrome c reductase as well as to a TPNH-oxidase. The possible significance of diaphorase in biological systems is discussed.