HEPATIC METABOLISM OF ALCOHOL BY GSH TRANSFERASES

三项研究的目的是描述一种新颖和令人兴奋的特征

The purpose of thee studies is to characterize a novel and exciting metabolic pathway for alcohol present in liver and related to carcinogen inactivation. Over the past eight years, the laboratory of the Principal Investigator has characterized nonoxidative alcohol metabolism in organs that are commonly injured by alcohol abuse, but often lack oxidative metabolism of alcohol. Based on these findings, he has described and purified to homogeneity two fatty acid ethyl ester synthases that catalyze the formation of fatty acid ethyl esters from ethanol. The major synthase was recently purified to homogeneity from human heart and its amino acid sequence reveals a remarkable degree of homology between it and hepatic glutathione S-transferase. This latter system is responsible for detoxifying a variety of drugs and carcinogens, but it has never been known to metabolize alcohol. Our studies presented in the Preliminary data section demonstrate that, in fact, the major fatty acid ethyl ester synthase is the first acidic GSH transferase to be purified to homogeneity and it can also catalyze the formation of GSH conjugates with a variety of drugs. In addition, GSH transferases from liver can catalyze the formation of fatty acid ethyl esters and substrates of the GSTs inhibit FAEE synthase. In this new R01 grant application, therefore, the Principal Investigator proposes to characterize the in vivo importance of nonoxidative metabolism in the liver by both biochemical and 13C NMR experiments. Subsequently, isoenzymes of the GSH transferases in liver capable of metabolizing alcohol into fatty acid ethyl esters will be identified. The potential modulation of fatty acid ethyl ester synthase activity or GSH transferase activity by commonly ingested drugs/carcinogens metabolized by the transferase system will be characterized. The inducibility of the transferases by ethanol feeding in the rabbit will be characterized. The goal of the proposed studies, therefore, reflects characterization of the GSH transferase as an alcohol-metabolizing system in liver which may be modulated by either environment or genetic factors. Since carcinogen inactivation by the transferases is a well recognized method of their transformation, studies bear importantly on the long- appreciated clinical association between alcohol abuse and tumor development.