Effects of various anions and cations on the release of four dehydrogenases from brain mitochondria by a non-ionic detergent.

Abstract

Summary It has been found that a number of agents greatly affects the release by Triton-X-ioo of certain dehydrogenases from rabbit-brain mitochondria. The enzymes studied were DPN-dependent isocitrate dehydrogenase ( L s-isocitrate:DPN+ oxidoreductase (decarboxylating), EC 1.1.1.41) and TPN-dependent isocitrate dehydrogenase ( L s-isocitrate:TPN+ oxidoreductase (decarboxylating), EC 1.1.1.42), gluta-mate dehydrogenase ( L -glutamate:DPN+ (TPN+) oxidoreductase (deaminating), EC 1.4.1.3) and lipoamide dehydrogenase (DPNH:lipoamide oxidoreductase, EC 1.6.4.3). The effects of Triton X-100 on the morphology of the mitochondria were checked with the electron microscope. 1. The detergent was shown to disrupt the architecture of the mitochondria, leaving single and double membranes and amorphous material. 2. ATP, ADP, pyrophosphate, citrate and isocitrate enhanced release of the enzymes. DPN was less effective, and α-ketoglutarate, adenylic acid and adenosine were ineffective, as was EDTA. 3. K+ and Na+ (80 mM) enhanced release of both isocitrate dehydrogenases, but partially prevented release of glutamate dehydrogenase. Ca2+ and Mg2+ at 4–5 mM enhanced release of TPN-isocitrate dehydrogenase but inhibited that of DPN-isocitrate dehydrogenase and glutamate dehydrogenase. Mg2+ had little effect on the release of lipoamide dehydrogenase. 4. It is suggested that metal ions play a role in the binding of these four dehydrogenases to the mitochondria, but that the details of the attachments may be different in each case.