Probably plays an important role in the regulation of erythrocyte shape and mechanical properties. Defects in EPB42 are the cause of spherocytosis type 5 (SPH5); also known as hereditary spherocytosis type 5 (HS5). Spherocytosis is a hematologic disorder leading to chronic hemolytic anemia and characterized by numerous abnormally shaped erythrocytes which are generally spheroidal. Absence of band 4.2 associated with spur or target erythrocytes has also been reported. Belongs to the transglutaminase superfamily. Transglutaminase family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.