Converts 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) to 2-succinylbenzoate (OSB) (PubMed:24872444). Also acts as a N-succinylamino acid racemase (NSAR) that catalyzes the racemization of N-succinyl-L-phenylglycine (PubMed:24872444). Since the gene is encoded in a menaquinone synthesis operon, OSB synthase is probably the physiological activity. A pathway that requires NSAR activity has not been identified in this species, so whether NSAR is also a biological activity is unknown (PubMed:24872444). (1R,6R)-6-hydroxy-2-succinyl-cyclohexa-2,4-diene-1-carboxylate = 2-succinylbenzoate + H2O kcat is 120 sec(-1) with SHCHC as substrate. kcat is 24 sec(-1) with N-succinyl-L-phenylglycine as substrate. Quinol/quinone metabolism; 1,4-dihydroxy-2-naphthoate biosynthesis; 1,4-dihydroxy-2-naphthoate from chorismate: step 4/7. Quinol/quinone metabolism; menaquinone biosynthesis. Homodimer. Belongs to the mandelate racemase/muconate lactonizing enzyme family. MenC type 2 subfamily.