Demonstration of cytochrome reductases in rat liver peroxisomes: biochemical and immunochemical analyses.

In this study we utilized the analytical cell fractionation approach in combination with immunoblotting techniques and immunoelectron microscopy to test for the presence of NADPH cytochrome P-450 reductase and NADH cytochrome c (b5) reductase in rat liver peroxisomes. Highly purified peroxisomes from clofibrate-treated rats exhibited both NADPH cytochrome P-450 reductase activity and NADH cytochrome c reductase activity (using cytochrome c as an electron acceptor). These activities were inhibited by the respective reductase antibodies made against the endoplasmic reticulum (ER) enzymes. Immunoblot data in combination with immunoelectron microscopy indicated that the peroxisomal NADPH cytochrome P-450 reductase is localized in the matrix of the organelle and has a subunit of molecular weight similar to that of the ER enzyme, whereas the NADH cytochrome c (b5) reductase is localized in the membranes of the peroxisomes. Again, the subunit molecular weight was similar to that of the ER enzyme. The presence of these reductases in peroxisomes further supports the role of this organelle in bile acid synthesis and cholesterol metabolism.