The Ca2+ -activated protease (calpain) modulates Ca2+/calmodulin dependent activity of smooth muscle myosin light chain kinase.
The Ca2+ -activated neutral protease can proteolyze both Ca2+ -dependent cyclic nucleotide phosphodiesterase and smooth muscle myosin light chain kinase. Ca2+ -dependent cyclic nucleotide phosphodiesterase from rat brain was converted to the Ca2+ -independent active form by Ca2+ -activated protease. The proteolytic effects on myosin light chain kinase of Ca2+-activated protease differed in the presence and absence of the Ca2+-calmodulin (CaM) complex. In the presence of bound CaM, myosin light chain kinase (130k dalton) was degradated to a major fragment of 62 kDa, which had Ca2+/CaM-dependent enzyme and CaM-binding activity. When digestion occurred in the absence of bound CaM, myosin light chain kinase cleaved to a fragment of 60 kDa. This peptide had no enzymatic activity in the presence or absence of the Ca2+-CaM complex. Available evidence suggests that the Ca2+-activated proteases may recognize the conformational change of smooth muscle myosin light chain kinase induced by Ca2+-CaM complex.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002154:Calpain / Q000378:metabolism*; D002645:Chickens; D004789:Enzyme Activation; D005895:Gizzard, Avian / Q000201:enzymology; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*
D002147:Calmodulin; D009219:Myosin-Light-Chain Kinase; D002154:Calpain; D002118:Calcium