Rate of the Enzymatic Breakdown of Digitoxin. ∗

Summary

A study of the breakdown of digitoxin to form digitoxigenin by hydrochloric acid and extracts of dried heart, liver, kidney, and yeast has been carried out. The results of this study showed the hydrochloric acid and extracts of heart and liver have the ability to cause this breakdown, while extracts of kidney and yeast are inactive in this reaction. Reaction rate studies gave the following rate constants at 29.7°C: 0.85%percnt; hydrochloric acid 6.85 × 10^-2, heart extract (10 g dried, defatted powder per 100 ml phosphate buffer) 5.15 × 10^-2, liver extract 5.80 × 10^-2 Purification of the heart extract yielded a reddish brown solid which had a high enzymatic activity and gave typical protein reactions.