Parvalbumin (PV) is a calcium-binding protein with low molecular weight. It is encoded by the PVALB gene. It has three EF hand motifs and is structurally related to calmodulin and troponin C. Parvalbumin is found in fast-contracting muscles, where its levels are highest, as well as in the brain and some endocrine tissues. Calcium binding proteins like parvalbumin play a role in many physiological processes, namely cell-cycle regulation, second messenger production, muscle contraction, organization of microtubules and phototransduction. Decreased PV and GAD67 expression was found in PV+ GABAergic interneurons in schizophrenia. Parvalbumin has been identified as an allergen causing fish allergy (but not shellfish allergy). Bony fishes manifest β-parvalbumin and cartilaginous fishes such as sharks and rays manifest α-parvalbumin; allergenicity to bony fishes has a low cross-reactivity to cartilaginous fishes.