CORRELATION BETWEEN THE ACTIVITY OF ACETALDEHYDE DEHYDROGENASE AND THE STRUCTURE OF MITOCHONDRIA

Abstract

This chapter discusses the correlation between the activity of acetaldehyde dehydrogenase and the structure of mitochondria. Hepatic oxidation of ethanol to acetate involves two oxidation steps, each catalyzed by an NAD-dependent enzyme. Most of the NADH generated during the metabolism of ethanol has to be oxidized by the mitochondrial electron transport chain, as cytoplasmic reactions are inadequate for reoxidation of NADH. Thus, the capacity of mitochondria to oxidize NADH becomes rate limiting in the overall metabolism of ethanol. In view of this importance of mitochondria in the oxidation reaction of NADH, the studies discussed in the chapter were undertaken to measure the rate of electron flux from acetaldehyde dehydrogenase located in the mitochondrial matrix to the cytochrome chain bound to the inner membrane, under various conditions. By employing very sensitive fluorometric and spectrophotometric techniques, redox changes of NADH and cytochrome c upon addition of acetaldehyde were monitored directly from intact mitochondria, without treatment with detergent or addition of an excess amount of exogenous NAD+. Thus, the characteristics of mitochondrial acetaldehyde dehydrogenase were explored under the condition that was more close to a native environment.