Isolation and characterization of NAD(P)H-dehydrogenases from seeds of the castor bean

Two pyridine nucleotide dehydrogenases have been isolated from castor bean seed extracts by a combination of ion exchange chromatography on DEAE-Sepharose and gel permeation chromatography on Sephadex G-200. The enzymes were designated D-I and D-II according to their elution position on DEAE-Sepharose. Both enzymes D-I and D-II are globular proteins which have MWs of 66 000 and 60 000, respectively. Dehydrogenation is observed with both NADH and NADPH as electron donors, while the electron acceptor specificity demonstrates that the enzymes are probably NAD(P)H: quinone oxidoreductases. Successful coupling of dehydrogenase activity with that of peroxidase indicates a possible role of the enzymes in seed germination.