Purification of new calcium activated protease (low calcium requiring form) and comparison to high calcium requiring form.

A new calcium activated protease which requires low concentration of calcium was purified to almost homogeneity from porcine heart muscle. The protease was composed of two polypeptide chains of approximately 90 K and 30 K. The 90 K subunit was larger than the large subunit of the high calcium requiring form of calcium activated protease, therefore we concluded that the low calcium requiring form is different from the high calcium requiring form and its auto-digested protease. The low calcium requiring form of calcium activated protease was also activated by manganese and balium, and was very stable even at pH 9.0.