TY - JOUR T1 - The Specific Binding of Vitamin A Acid to Equine Liver Alcohol Dehydrogenase JF - Molecular Pharmacology JO - Mol Pharmacol SP - 199 LP - 208 VL - 9 IS - 2 AU - JOHANNES EVERSE Y1 - 1973/03/01 UR - http://molpharm.aspetjournals.org/content/9/2/199.abstract N2 - Addition of vitamin A acid to solutions of liver alcohol dehydrogenase (EC 1.1.1.1) results in a significant quenching of the protein fluorescence. The quenching attains a maximum value when equimolar amounts of the reactants are present. The quenching is pH-dependent, and indicates the involvement of a group on the protein with a pK value of 7.6. Vitamin A acid is a competitive inhibitor of the oxidation of ethanol, but does not significantly affect the reverse reaction. On the other hand, vitamin A amide competitively inhibits the reduction of acetaldehyde, without significantly affecting the oxidation of ethanol. The vitamin A acid protects the essential thiol groups against carboxymethylation to a lesser degree than reduced coenzymes but to a higher degree than ethanol. ACKNOWLEDGMENTS It is a pleasure to thank Professor N. O. Kaplan for his support and encouragement during this work. The author is also indebted to Dr. P. H. van Leeuwen, N. V. Philips-Duphar, Weesp, The Netherlands, for his generous gift of the crystalline vitamin A acid isomers and the all-trans vitamin A aldehyde. ER -