Two new complexes, [M (AB)(2)(CP)(2)(H2O)(2)] (where M = Ni and Co AB = 4-aminobenzoate and CP = cyanopyridine), were synthesized and characterized using different techniques (elemental analysis, FT-IR spectrophotometer, LC/MS, single-crystal X-ray diffraction, and TGA/DTA analysis). As a result of X-ray structural analysis, it was determined that complexes are isostructural. In the crystalline structures, M-II ions are bridged with their carboxylate oxygen and aminopyridine nitrogen atoms and their symmetry-related counterparts to form a two-dimensional polymeric structure. The M-II ion is octa-coordinated with two nitrogen atoms and two oxygen atoms of the AB and two atoms of the CP anions. In this study, the effect of these molecules, containing a biologically active group, was investigated on important metabolic enzymes (carbonic anhydrase isoenzymes I and II (hCA I and II), achethylcholinesterase (AChE), and alpha-glycosidase (alpha-Gly) enzymes).