title: Understanding nature's strategies for enzyme-catalyzed racemization and epimerization.
abstract: Epimerases and racemases are enzymes that catalyze the inversion of stereochemistry in biological molecules. In this article, three distinct examples are used to illustrate the wide range of chemical strategies employed during catalysis, and the diverse set of ancestors from which these enzymes have evolved. Glutamate racemase is an example of an enzyme that operates at an "activated" stereocenter (bearing a relatively acidic proton) and employs a nonstereospecific deprotonation/reprotonation mechanism. UDP-N-Acetylglucosamine 2-epimerase acts at an "unactivated" stereocenter and uses a mechanism involving a nonstereospecific elimination/addition of UDP. L-Ribulose phosphate 4-epimerase also acts at an unactivated stereocenter and uses a nonstereospecific retroaldol/aldol mechanism.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Tanner
mesh_terms: D002384:Catalysis; D020134:Catalytic Domain; D018716:Molecular Mimicry; D011487:Protein Conformation; D019998:Racemases and Epimerases / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D019998:Racemases and Epimerases