The CA8 (CARP) gene encodes carbonic anhydrase VIII, which is part of a family of zinc metalloenzyme. CA8 has a central carbonic anhydrase motif, but it lacks carbonic anhydrase activity due to absence of catalytic zinc coordinating residues(PMID:2121526). CARP is a novel IP3R1-binding protein, and is expressed in Purkinje cells abundantly. CA8 is co-localized with IP3R1 in Purkinje cells and it binds to IP3R1, reducing the affinity of the receptor for its ligand, IP3(PMID:12611586). Defects in CA8 are the cause of cerebellar ataxia mental retardation and dysequilibrium syndrome type 3 (CMARQ3)(PMID:19461874).