The invention disclosed herein relates to novel synergistic medicinal compositions for treating dysfunctional D-serine (DSR) signaling. Particularly the invention provides potent synergistic medicinal composition comprising combination of N-acetyl taurinate salt of divalent metal (M2+AT) as serine racemase enzyme (SR) activator/stimulator and benzoic acid ester salt of monovalent or divalent metals (M+/2+Bz) as d-amino acid oxidase enzyme (DAAO) inhibitor, which are present in weight ratio of 1:0.001 to 1:1.5 along with pharmaceutically acceptable excipients. Further the present synergistic medicinal composition is useful for treating certain neuropsychiatric disorders, neurological disorders and metabolic disorders.