NADH-SPECIFIC DEHYDROGENASE FROM ONION ROOT PLASMA-MEMBRANE - PURIFICATION AND CHARACTERIZATION

Plasma membranes isolated from onion roots by two-phase partition cont ain at least two different NAD(P)H-dehydrogenases. A 27 kDa electron t ransport protein oxidises both NADH and NADPH and exhibits maximal act ivity with quinones as electron accepters. A distinct 31 kDa dehydroge nase is specific for NADH as donor and shows maximal activity with fer ricyanide. This novel enzyme is responsible for most NADH-ferricyanide oxidoreductase activity of solubilized onion root plasma membranes an d exhibits properties different to other purified NAD(P)H-dehydrogenas es