Probing the Active Site of Yeast Alcohol Dehydrogenase through Microscale Yeast-Mediated Reductions of Acetophenone and Acetylpyridines. A Collaborative and Research-Based Advanced Bioorganic Chemistry Laboratory Project

A collaborative and research-oriented advanced bioorganic chemistry project that probed the structure and reactivity relationship of yeast alcohol dehydrogenase (YADH) is reported. The project involved microscale and stereoselective reductions of acetophenone and 2-, 3-, and 4-acetylpyridines by yeast. Each pair of students was assigned two substrates to ensure duplication of each individual experiment, and the results were combined. At the end of the project, each student had to prepare a detailed report based on the entire set of results. The acetylpyridines being better substrates than acetophenone was consistent with the polar nature of the active site of YADH. The major enantiomer of the optically active secondary alcohols was (S) in all cases, and that was also consistent with the transfer of a hydride ion from NADH to the re-face of the prochiral carbonyl group. The results showed 4-acetylpyridine to be the best substrate for product formation and asymmetric induction. This observation is presumably a result of favorable hydrogen bonding interactions between the pyridyl-N atom and the hydroxy group of Tyr-140 in the substrate binding site of the enzyme. A collaborative and research-oriented advanced bioorganic chemistry project that probed the structure and reactivity relationship of yeast alcohol dehydrogenase (YADH) is reported. The project involved microscale and stereoselective reductions of acetophenone and 2-, 3-, and 4-acetylpyridines by yeast. Each pair of students was assigned two substrates to ensure duplication of each individual experiment, and the results were combined. At the end of the project, each student had to prepare a detailed report based on the entire set of results. The acetylpyridines being better substrates than acetophenone was consistent with the polar nature of the active site of YADH. The major enantiomer of the optically active secondary alcohols was (S) in all cases, and that was also consistent with the transfer of a hydride ion from NADH to the re-face of the prochiral carbonyl group. The results showed 4-acetylpyridine to be the best substrate for product formation and asymmetric induction. This observation is presumably a result of favorable hydrogen bonding interactions between the pyridyl-N atom and the hydroxy group of Tyr-140 in the substrate binding site of the enzyme