The Effect of Ethanol and Its Metabolites Upon Methionine Synthase Activity In Vitro

• Published in: Alcohol (Fayetteville, N.Y.) Vol. 15; no. 4; pp. 305 - 309
• Main Authors: Kenyon, Susan H, Nicolaou, Anna, Gibbons, William A
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.05.1998; Elsevier Science
• Subjects: 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase - antagonists & inhibitors; 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase - metabolism; Acetaldehyde; Acetaldehyde - pharmacology; Acetates - pharmacology; Alcoholism and acute alcohol poisoning; Animals; Biological and medical sciences; Cobalamin; Ethanol; Ethanol - metabolism; Ethanol - pharmacology; Homocysteine; Medical sciences; Methionine; Methionine synthase; Osmolar Concentration; Rats; Time Factors; Toxicology; Cobalamin; Methionine synthase; Ethanol; Homocysteine; Methionine; Acetaldehyde; O-Acetylhomoserine (thiol)-lyase; Rat; Enzyme; Metabolite; Toxicity; Rodentia; Metabolism toxicity relation; Lyases; Acetate; In vitro; Vertebrata; Mammalia; Enzymatic activity; Animal; Mechanism of action; Carbon-oxygen lyases
• ISSN: 0741-8329; 1873-6823
• DOI: 10.1016/S0741-8329(97)00134-1

The association of alcoholism with macrocytic anaemia has lead to investigation of the role of cobalamin-dependent methionine synthase in mediating alcohol toxicity. Several studies have found that long-term ingestion of large quantities of ethanol causes inhibition of liver methionine synthase activity in vivo; however, ethanol has not been found to inhibit the enzyme directly. The effect of ethanol and its breakdown products, acetate and acetaldehyde, on highly purified rat liver methionine synthase was tested in vitro. Enzyme activity was not inhibited by ethanol or acetate. Acetaldehyde was found to inhibit methionine synthase activity, with an apparent IC 50 of 2 mM. The reported inhibition by acetaldehyde was found to become irreversible over time. Acetaldehyde-induced inhibition of liver methionine synthase activity is thus proposed as the most likely explanation of the reported in vivo effect of ethanol upon methionine synthase.