Projekat ljudskog genoma je pokazao da postoji više deset kalpainskih izoformi, neke od koji imaju višestruke splajsne varijante.[2][3][4] Kao prvi kalpain čija trodimenzionalna struktura je određena, m-kalpain je prototipna proteaza C2 (kalpainske) familije u MEROPS bazi podataka.
^Cuerrier D, Moldoveanu T, Davies PL (2005). „Determination of peptide substrate specificity for mu-calpain by a peptide library-based approach: the importance of primed side interactions”. J. Biol. Chem.280 (49): 40632—41. PMID16216885. doi:10.1074/jbc.M506870200.
^Thompson V (2002-02-12). „Calpain Nomenclature”. College of Agriculture and Life Sciences at the University of Arizona. Приступљено 2010-08-06.
^Suzuki K, Hata S, Kawabata Y, Sorimachi H (2004). „Structure, activation, and biology of calpain”. Diabetes. 53. Suppl 1: S12—8. PMID14749260. doi:10.2337/diabetes.53.2007.s12.
Liu J, Liu MC, Wang KK (2008). „Calpain in the CNS: from synaptic function to neurotoxicity”. Sci Signal. 1 (14): re1. PMID18398107. doi:10.1126/stke.114re1.
Suzuki K, Hata S, Kawabata Y, Sorimachi H (2004). „Structure, activation, and biology of calpain”. Diabetes. 53. Suppl 1: S12—8. PMID14749260. doi:10.2337/diabetes.53.2007.s12.
Yuen PW, Wang KW (1999). Calpains : Pharmacology and Toxicology of a Cellular Protease. Boca Raton: CRC Press. ISBN1-56032-713-8.