Action of Crude Papain on Actin and Myosin Heavy Chains Isolated From Chicken Breast Muscle

The individual myofibrillar proteins, myosin and actin, were digested with crude papain (1:125 w/w for 0–3 min). The sodium dodecyl sulfate electrophoretic patterns and the rate of proteolytic hydrolysis were observed. Actomyosin, natural actomyosin and both contracted and uncontracted glycerinated myofibrils were also studied. It was found that the gel pattern of the actin proteolytic digestion suggested that two populations of actin exist; that although actin had the highest rate of hydrolysis in the pH stat, the gels suggested only a very limited proteolysis; that actomyosin is less rapidly digested than myosin; and that the proteins of the myofibrils, especially when contracted, are rapidly cleaved.