Catalyzes the dehydration of D-tartrate to oxaloacetate. (S,S)-tartrate = H2O + oxaloacetate Binds 1 Mg(2+) ion per subunit. kcat is 7.3 sec(-1) for D-tartrate. Homooctamer; tetramer of dimers. Reaction mechanism is a simple extension of the two-step reaction catalyzed by other members of the family: Lys-184 initiates the reaction by abstraction of the alpha-proton to generate a Mg(2+)-stabilized enediolate intermediate, and the vinylogous beta-elimination of the 3-OH group is general acid-catalyzed by the His-322, accomplishing the anti-elimination of water. The replacement of the leaving group by solvent-derived hydrogen is stereo-random, suggesting that the enol tautomer of oxaloacetate is the product (PubMed:17144653). Belongs to the mandelate racemase/muconate lactonizing enzyme family.