Cytochrome b5 and Cytochrome b5 Reductase from a Chemical and X-Ray Diffraction Viewpoint

The endoplasmic reticulum of mammalian liver cells contains two major electron-transport enzyme systems. One of these is the NADH-linked cytochrome b 5 system which catalyzes the desaturation of fatty acids. The other is the NADPH-linked cytochrome P-450 system which catalyzes the hydroxylation of steroids, drugs, carcinogens, and other lipid-soluble substances. Although there is some interaction between these two systems (Lu et al., 1974) the following discussion will limit itself to the cytochrome b 5 system.