2-(3-Amino-pyridinium-1-yl)-3-carb-oxy-propano-ate monohydrate.

The title compound, C(9)H(10)N(2)O(4)·H(2)O, was obtained as a zwitterion derived from the nucleophilic attack of 3-amino-pyridine on the fumaric α,ß-system. Within the molecule, the amino-pyridine moiety and the carboxyl-ate and carb-oxy-lic acid fragments form dihedral angles of 68.6 (2) and 62.8 (2)°, respectively. The geometry adopted by the mol-ecule does not allow the formation of centrosymmetric dimeric hydrogen-bonded units; instead chains along the a axis are linked by COO-H⋯OOC motifs. These chains are inter-connected by N-H⋯O and O-H⋯O hydrogen bonds involving the carb-oxy-lic acid and carboxyl-ate units and the solvent water mol-ecules.