Purification and partial characterization of a trypsin inhibitor from chick skeletal muscle

A protein capable of inhibiting trypsin and a number of other serine proteases was purified from chicken skeletal muscle. It has an apparent molecular weight of 64.000 as determined by gel filtration. The inhibitor molecule binds trypsin at a molar ratio of 1:1 to form a stable complex, in which trypsin can be completely inhibited. In this complex. the inhibitor is extensively digested by trypsin but retains its inhibitory activity and tertiary structure by intramolecular disulfide bonds. In addition, its activity was found to markedly increase during development of embryonic muscle. The physiological role of this inhibitor, however, remains unknown.