Effect of high hydrostatic pressure on the conversion of alpha-connectin to beta-connectin

The factors affecting the conversion of alpha-connectin to beta-connectin induced by pressurization of muscle were investigated over a pressure range from 100 to 400 MPa by using SDS-PAGE and immunoblot analysis. When muscles were exposed to high pressures, the conversion of alpha-connectin to beta-connectin was the most pronounced at a pressure of 300 MPa, and the appearance of 1,200-kDa peptide accompanied by conversion of alpha- to beta-connectin was observed. Connectin was relatively resistant to degradation under a pressure of 400 MPa. The degradative products of beta-connectin reactive with mAb 2D4 were not observed. The effect of high pressure on connectin in isolated myofibrils was similar to that on connectin in muscle. Addition of leupeptin and E-64 to the isolated myofibrils resulted in the prevention of the degradation of connectin at each stage of the pressurization. The ability of calcium-activated protease (calpain) to hydrolyze connectin from alpha to beta gradually declined with increasing pressure. The results indicate that calpain is responsible for the pressure-induced conversion of alpha- to beta-connectin. The rate of this conversion is probably regulated by the pressure-dependent structural change of alpha-connectin and inactivation of calpain.