[Acid proteinase of chicken liver. Purification and properties (author's transl)]

A method for purifying the haemoglobinolitic activity to acid pH in chicken liver is described. The purified preparation contains cathespin D activity since it is inhibited by diazoacetyl-DL-norleucine methylester in the presence of cupric ions, while thiol-enzyme reagents do not affect it. The molecular weight of the enzyme is approximately 40,000--45,000 and the pH optimum against haemoglobin and bovine serum albumin is 3.5-3.7. The rate of degradation of albumin and casein is much less than that of haemoglobin. Cathepsin D preparations with different purification degrees, exhibit a similar percentage of activation at acid pH; the highest activation is observed at pH 3.1-3.3.