A rapid, large-scale method for purification of the metallo-carboxypeptidase inhibitor from potato tubers.

A rapid, large-scale procedure has been developed for the preparation of metallo-carboxypeptidase inhibitor (CPI) from potatoes. The inhibitor is extracted with 80% ethanol from partially cooked potato tubers. After the ethanol is removed and the salts are dialyzed away, the inhibitor is isolated in pure form by chromatography on sulfopropyl Sephadex. Ten pounds of potatoes yields 250 mg pure inhibitor, representing over 40% recovery. Commercial mashed potato flakes contain about 0.02% carboxypeptidase inhibitor and can be utilized as a starting material in the procedure described to yield over 70 mg inhibitor from a pound of flakes.