Investigating Enzyme Active-Site Geometry and Stereoselectivity in an Undergraduate Biochemistry Lab

The three-dimensional nature of interactions between enzymes and their substrates often leads to exacting spatial binding orientations and stereoselectivity in chemical catalysis. Dehydrogenases that use NAD+ as a redox cofactor tend to show stereospecificity in transferring a hydride to the C4 of the nicotinamide moiety via either the re or the si face. The stereospecificity of this hydride transfer, which results in a prochiral C4 in the reduced NADH, may be determined using deuterated substrates and 1H NMR spectroscopy. A biochemistry lab activity that combines analysis of the intermolecular interactions and spatial orientation between substrate, cofactor, and enzyme from a recent crystal structure of yeast alcohol dehydrogenase with improved in situ single-tube reaction conditions for elucidating the prochiral specificity of yeast alcohol dehydrogenase through 1H NMR spectra analysis is presented.