Calcium-regulated non-lysosomal thiol-protease. Activated by millimolar concentrations of calcium. Translocates to intracellular membranes when calcium levels are increased. Strongly expressed in follicular and border cells of the oocyte. Ubiquitously expressed in early embryos. Localized to the trachea and their orifices, and to the larynx of late embryos. Restricted to the salivary gland in third instar larvae. Expressed in all developmental stages, with highest expression in the egg, probably of maternal origin. Very low expression in the early larva, rising through larval development up to the third larval stage. Constant expression in the pupa and adult. Undergoes calcium-dependent autolytic cleavage between Asn-74 and Ala-75 and between Gln-224 and Asn-225 to produce two major products, calpain B catalytic subunit 1 and calpain B catalytic subunit 2. This autolysis is necessary for activation of the protein. Belongs to the peptidase C2 family.