Rapid scan spectrometry: oxidation of substrates by coupled potato mitrochondria

Abstract

By rapid scan spectrometry, spectral changes of redox components have been followed during the oxidation of substrates by coupled potato (Solanum luberosum L. cv. Bintje) mitochondria under different redox conditions. The redox changes of the b cytochromes, the changes in the base line level and in the slope of the spectra during aerobiosis appear to be connected with changes of the membrane potential. As the latter does not collaps at anaerobiosis, cytochrome o3 remains in an oxidized state. Collapse of the membrane potential by uncouplers induces partial oxidation of the b cytochromes and reduction of cytochrome a 3, so that toe resulting redox states derive from thermodynamic equilibrium with the redox conditions of the substrates. However, in aerobiosis as well as in anaerobiosis, the amplitude changes of the b cytochromes vary with the substrate oxidized as if these components were not always completely connected with the cytochrome oxidase complex. The b cytochromes become fuliy reduced only after dithionite reduction.