[56] DT diaphorase

TLDR: DT diaphorase is a flavin adenine dinucleotide (FAD)-eontaining flavoprotein, which catalyzes the oxidation of NADH and NADPH by various dyes and quinones with a maximal velocity of the order of 10 7 moles per mole of flavin per minute.

Abstract: Publisher Summary DT diaphorase is widely distributed in the animal kingdom, and is a flavin adenine dinucleotide (FAD)-eontaining flavoprotein, which catalyzes the oxidation of NADH and NADPH by various dyes and quinones with a maximal velocity of the order of 10 7 moles per mole of flavin per minute. Bovine serum albumin (0.07%), polyvinylpyrrolidone (5%), and certain nonionic detergents such as Tween-20 or -60 (0.2%) are activators of DT diaphorase; the concentrations in parentheses are those required for maximal activation. The activation is reversible and implies both an elevation of the V max of the enzyme and an increase of its affinity for NADH and NADPH. The need for an activator increases during the purification and storage of the enzyme, probably because of the removal or destruction of a naturally occurring activator. Various electron acceptors for DT diaphorase are listed. 2, 6-Diehlorophenolindophenol (DCPIP) and certain benzo- and naphthoquinones are the best electron acceptors, whereas methylene blue and ferricyanide are relatively inefficient, and cytochromes c and b 5 are practically inactive as electron acceptors. The chapter also describes the assay and purification procedure of DT diaphorase, and discusses the DT diaphorase relation to other diaphorases and related enzymes.