Epimerase and racemase

Epimerases and racemases are isomerase enzymes that catalyze the inversion of stereochemistry in biological molecules.{{cite journal | author = Tanner, ME. | title = Understanding nature's strategies for enzyme-catalyzed racemization and epimerization | journal = Acc. Chem. Res. | year=2002 | volume=35 | issue=4 | pages=237–246 | pmid = 11955052 | doi = 10.1021/ar000056y }}

Racemases catalyze the stereochemical inversion around the asymmetric carbon atom in a substrate having only one center of asymmetry. Epimerases catalyze the stereochemical inversion of the configuration about an asymmetric carbon atom in a substrate having more than one center of asymmetry, thus interconverting epimers.

Human epimerases include methylmalonyl-CoA epimerase, involved in the metabolic breakdown of the amino acids alanine, isoleucine, methionine and valine,{{Cite web|url=http://www.britannica.com/science/isomerase|title = Isomerase | enzyme | Britannica}} and UDP-glucose 4-epimerase, which is used in the final step of galactose metabolism - catalyzing the reversible conversion of UDP-galactose to UDP-glucose.