Alcohol and aldehyde dehydrogenases in the gastrointestinal trac

© 1996 by Taylor & Francis. The existence of ethanol metabolism in the gastrointestinal tract depends on the presence of suitable enzymatic systems to oxidize the alcohol to aldehyde. These systems are the microsomal cytochrome P-450 dependent system, catalase, and alcohol dehydrogenase. These three systems exist in the gastrointestinal tract, although their relative contribution is still controversial. Recently, different levels of alcohol dehydrogenase activity and different enzyme forms in the various digestive organs have been described, suggesting that they can be sites of active ethanol 42oxidation. The second step in ethanol metabolism, the oxidation of acetaldehyde to acetic acid, can be also locally performed due to the presence of aldehyde dehydrogenase in the gastrointestinal tract. This chapter describes the functional and structural characteristics of the gastrointestinal forms of both dehydrogenases and their distribution in human gut. Data from the rat species are also included where the corresponding information from the human enzyme is not available.