title: Cytochrome components of plant microsomes.
abstract: The electron transport components of the microsomal fraction of cauliflower buds and mung bean hypocotyls were investigated using split-beam and dual wavelength spectrophotometry under a variety of reducing conditions. Cauliflower microsomes were found to contain an ascorbate-reducible component, termed cytochrome b-559.5 [E'0 = +135 +/- 20 mV; lambdamax (reduced minus oxidised) = 559.5, 527 and 429 nm at 23 degrees C], cytochrome b5 [E'0 = -20 +/- 20 mV; lambdamax (reduced minus oxidised) = 556, 526 and 425 nm at 23 degrees C], cytochromes P-450 and P-420. On the basis of binding studies with ethyl isocyanide, degradation of cytochrome P-450 to P-420, redox potential, aniline binding, and relative rates of reduction by NADPH and NADH, it is suggested that the cytochrome P-450 system is analogous to that mammalian microsomes. Other components, reducible only by dithionite, may also be present. Mung bean microsomes were found to contain an ascorbate-reducible component, termed cytochrome b-562 [E'0 = +120 +/- 20 mV; lambdamax (reduced minus oxidised) = 562, 528 and 430 nm at 23 degrees C], cytochrome b5, and a low potential component which was reducible only by sodium dithionite. No cytochrome P-450 or P-420 could be detected. A general method of analysis of the cytochromes was developed and applied to the microsomes from a variety of plant sources. The results indicate that large variations, both in type and amount of components, occur between the microsomes from different plant materials.
mesh_terms: D000814:Aniline Compounds; D002248:Carbon Monoxide; D003579:Cytochrome Reductases / Q000032:analysis; D003580:Cytochromes / Q000032:analysis*; D004579:Electron Transport; D008861:Microsomes / Q000201:enzymology*; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology*; D011485:Protein Binding; D013045:Species Specificity; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D000814:Aniline Compounds; D003580:Cytochromes; D002248:Carbon Monoxide; D003579:Cytochrome Reductases