Lyophilized Escherichia coli membranes lose 50% of their DPNH oxidase activity when exposed to O2. The oxidation of succinate or lactate is not affected by this treatment. The enzyme damaged by O2 is the membrane DPNH dehydrogenase (DPNH-ferricyanide oxidoreductase, EC 126.96.36.199). The Km values for DPNH and the electron acceptor K3Fe(CN)6 are the same in the native and the inactivated enzyme. The vmax of the latter is decreased by 50% for both substrates. The accessibility of non-heme iron to o-phenanthroline is partly increased. It is suggested that the non-heme iron of DPNH dehydrogenase participates in intramolecular electron conductance between the oxidizing and the reducing sites of the enzyme.
|Number of pages||5|
|Journal||Biochimica et Biophysica Acta - Bioenergetics|
|State||Published - 8 Apr 1969|