The Ca2+-dependent proteolytic system—Calpain-calpastatin—In the neural tissue of the honeybee Apis mellifera

Ca²⁺-dependent proteinase activity was detected in the neural tissue of the honeybee Apis mellifera. DEAE-chromatography revealed two Ca²⁺-dependent proteinase activities, with elution positions corresponding to vertebrate calpain I and II. Both activities yielded apparent $\text{M}{}_{\mathrm{<mtext>r</mtext>}}\text{= 80,000}$, had a strict requirement for Ca²⁺ and a SH-reducing agent. PMSF and trypsin inhibitor did not affect the proteinase activities. Alkylating agents and mercaptide forming compounds as well as the calpain inhibitor calpastatin purified from bovine brain inhibited the activity. The natural inhibitor protein detected in the neural tissue of the honeybee showed properties equal to calpastatin from other sources. All observed properties are in accordance with those of the Ca²⁺-dependent proteolytic system calpain-calpastatin.