Limited Autolysis of Ca2+-Activated Neutral Protease (CANP) Changes Its Sensitivity to Ca2+ Ions

Abstract

Ca2+-activated neutral protease (CANP) usually requires mM Ca2+ for activation. The sensitivity of CANP to Ca2+ is greatly enhanced by passing it through a casein-Sepharose column in the presence of Ca2+ ions. This conversion is ascribed to autolysis of CANP. The converted enzyme required 40 microM Ca2+ for 50% activation. Various properties of the converted enzyme were very similar to those of CANP-I, recently found in canine heart muscle. Names of "m-CANP" and "mu-CANP" are proposed for CANPs which require mM and microM order Ca2+ for inactivation, respectively.

Postmortem protein degradation is a key contributor to fresh pork loin tenderness

“…Activation of calpain-1 is closely coupled with autolysis (Baki et al, 1996). Autolysis lowers the amount of calcium needed for activation of calpain-1 (Suzuki et al, 1981). Calpain-1 in muscle degrades the proteins desmin, troponin-T, and titin during postmortem aging in beef (Huff-Lonergan et al, 1996a) and pork (Lonergan et al, 2001;Melody et al, 2004).…”

Regulating cell migration: calpains make the cut

“…The best-studied mechanism is activation by calcium -hence the name calpain (Guroff, 1964). In fact, calpain 1 and calpain 2 are commonly referred to by their in vitro requirements for calcium: calpain 1 ( -calpain) is activated by micromolar calcium concentrations and calpain 2 (m-calpain) requires millimolar concentrations (Suzuki et al, 1981b). Because calpains contain calcium-binding EF-hand motifs in domains IV and VI and, because domain IV of calpain 1 and domain IV of calpain 2 are different, these were originally presumed to be responsible for the calciumdependent activation of calpains.…”

“…The large subunits of some calpains are autolyzed on activation, which removes domain I and abolishes the N-terminal link between the large and small subunits, thereby allowing movement of domain II (Baki et al, 1996;Cong et al, 1989;Elce et al, 1997;Guttmann et al, 1997;Imajoh et al, 1986;Molinari et al, 1994;Suzuki and Sorimachi, 1998;Suzuki et al, 1981a). The truncated large subunit is catalytically active and has a lower requirement for calcium (Baki et al, 1996;Imajoh et al, 1986;Suzuki and Sorimachi, 1998;Suzuki et al, 1981b). However, this event is clearly not required for catalytic activity (Cong et al, 1989;Elce et al, 1997;Guttmann et al, 1997;Molinari et al, 1994), which suggests that it functions more in the progression of activation than in its initiation.…”

Structural modifications associated with the change in Ca2+ sensitivity on activation of m‐calpain

“…On binding Ca*' to the calmodulin-like domains at the C-tern&i of the subunits, calpains become active and begin to self-digest (autolyse). One consequence of autolysis is a change in the Ca*+ sensitivity of calpains; the enzymes become active at lower Ca*+ concentrations [2,3]. The change in Ca*+ sensitivity has been proposed to play a role in enzyme activation in vivo [4].…”