Characterization and partial purification of multiple electron transport activities in plasma membranes from maize (Zea mays) roots

The plasma membrane of eukaryotic cells contains endogenous, integral electron transport proteins. In the maize ( Zea mays L. cv. Golden Cross Bantam) root plasma membrane, these activities include NAD(P)H‐ferricyanide reductase. NAD(P)H‐duroquinone reductase (1.6.5.1) and NAD(P)H‐ascorbate free‐radical reductase (EC 1.6.5.4). Differences in degree of stimulation upon vesicle rupture with detergent and in specificities for pyridine nucleotides suggest that these activities constitute distinct components in the membranes. Solubilization of reductase activities was examined using Triton X‐100 over a wide range of retergent‐to‐protein ratios. The Triton‐solubilized enzymes were purified using dye‐ligand affinity chromatography on Cibacron blue 3G‐A agarose utilizing biospecific elution with NADH. Resolution of the redox activities was accomplished upon differential elution with 0.1.1.0 and 10 m M NADH. The distinctive characteristics of the enzymes and the differential chromatographic behavior of the respective activities provided evidence for the presence of separate enzymatic redox components in maize root plasma membranes with implications for an electron transfer chain.