In enzymology, a protein-serine epimerase () is an enzyme that catalyzes the chemical reaction
Hence, this enzyme has one substrate, [protein]-L-serine, and one product, [protein]-D-serine.
This enzyme belongs to the family of isomerases, specifically those racemases and epimerases acting on amino acids and derivatives. The systematic name of this enzyme class is [protein]-serine epimerase. This enzyme is also called protein-serine racemase.
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .