The CA8 gene encodes carbonic anhydrase VIII (CARP VIII), which is part of a family of zinc metalloenzymes that catalyze the reversible hydration of bicarbonate. Although CA8 has a central carbonic anhydrase motif, it lacks classical carbonic anhydrase activity (i.e., the reversible hydration of carbon dioxide) due to the absence of one or more histidine residues required for binding to the zinc ion, which is critical for CO2 hydration activity. Nonetheless, the gene product continues to carry a carbonic anhydrase designation because it showed a clear sequence identity to other members of the carbonic anhydrase gene family. The absence of CA8 gene transcription in the cerebellum of the “lurcher” mutant in mice with a neurologic defect suggests an important role for this acatalytic form. The sole known biochemical function of CA8 is to inhibit inositol 1,4,5-triphosphate (IP3) binding to IP3 receptor 1 (ITPR1). However, the exact biological function of CA8 is still unknown.