[Action of muscular proteinases on fast and slow myosins. Relation with post-mortem proteolysis in muscles of variable contractility].

Sensitivity to proteolysis of fast and slow rabbit skeletal muscle myosins with cathepsins D, B, H and L and with calpains I and II was studied in various incubation conditions. Cathepsins D, B and L degraded both myosins and exhibited different specificities towards these proteins. Moreover, in each case slow myosin appeared to be less sensitive to proteolysis than fast myosin. This finding agrees well with the lower extent of protein hydrolysis observed during post-mortem ageing of meat in slow twitch pork muscles.