NADH-specific dehydrogenase from onion root plasma membrane: purification and characterization

Summary Plasma membranes isolated from onion roots by twophase partition contain at least two different NAD(P)H-dehydrogenases. A 27 kDa electron transport protein oxidises both NADH and NADPH and exhibits maximal activity with quinones as electron acceptors. A distinct 31 kDa dehydrogenase is specific for NADH as donor and shows maximal activity with ferricyanide. This novel enzyme is responsible for most NADH-ferricyanide oxidoreductase activity of solubilized onion root plasma membranes and exhibits properties different to other purified NAD(P)H-dehydrogenases.Abbreviations DES diethylstilbestrol - FeCN potassium ferricyanide - NBT nitroblue tetrazolium - PHMB p-hydroxymercuribenzoate - PMSF phenylmethylsulfonylfluoride - PTA phosphotungstic acid - SHAM salicylhydroxamic acid - TTFA thenoyltrifluoroacetone