Dr. Rodney P Guttmann

Calpains play important roles in numerous physiological and pathological processes (1,2) by catalyzing the limited proteolysis of a wide variety of protein substrates. The activity of calpain toward a specific substrate is regulated not only by calcium, but also by numerous other factors including calpain activator proteins (3), redox state (4,5), and the phosphorylation state of the substrate (6, 7, 8). In order to determine the relative contributions of these and other factors to the activity of calpain, it is necessary to be able to measure calpain activity both in vitro and in situ, and these assays are the subject of this chapter.