D-stereoisomers of amino acids are synthesized from L-stereoisomers by amino acid racemases which catalyze a proton-transfer reaction to invert a chiral center C(alpha) of an amino acid. Crystal Structure of PLP-independent Putative Aspartate Racemase from Salmonella Typhimurium was solved at 1.8A resolution. Its function is independent of metals or cofactors and two cysteins in the active site work as acid and base for racemization assisted by several other residues from the active site. Protein has two structurally very similar domains in a pseudo symmetrical arrangement (residues 1-110, 215-244 form N-terminal and 111-214 - C-terminal domains) situated at approximately 90o to each other. The active site of the protein is situated between domains, where ligand is positioned in the center of the pseudo-symmetry.