[Acid proteases from chicken liver. Cooperative hydrolysis of proteins (author's transl)]

Purified preparations of cathepsin D, BANA-hydrolase activity and dipeptidil aminopeptidase I from chicken liver, show a cooperative effect in the protein hydrolysis (acid-denatured haemoglobin and bovine serum albumin and native bovine serum albumin) at pH 5.0. The nature of the protein substrates determines their sensitivity to enzymatic digestion. The action of cathepsin D on proteins, in contrast which the BANA-hydrolase activity, releases polypeptides with high molecular weight, with scant--NH2 groups which can be valued by the ninhydrin method. These peptide fragments can then be further degraded by the protease BANA-hydrolase and the dipeptidil aminopeptidase I which is not active towards intact proteins.