Purification and Characterization of Microsomal Cytochrome b5 and NADH Cytochrome b5 Reductase from Pisum sativum

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Abstract
In this communication we document the reproducible protocols for the purification of milligram quantities of cytochrome b5 and NADH-cytochrome b5 reductase from the microsomal fraction of Pisum sativum. The cytochrome b5 component of this NADH linked electron transport chain was found to have a molecular mass of 16,400 daltons and the reductase a molecular mass of 34,500 daltons. These components could be reconstituted into a functional NADH oxidase activity active in the reduction of exogenous cytochrome c or ferricyanide. In the latter assay the purified reductase exhibited a turnover number of 22,000 per minute. The amino-terminal amino acid sequence of the cytochrome b5 component was determined by sequential Edmund degredation, thus providing crucial information for the efficient cloning of this central protein of plant microsomal electron transfer.