1. The Barrett (1967) assay for cathepsin D was slightly modified. 2. The enzyme was purified from liver of man and chicken by a procedure involving autolysis, acetone fractionation, ion-exchange chromatography and isoelectric focusing. 3. Several isoenzymes of cathepsin D were resolved in the isoelectric-focusing step, and three major forms, α,β and γ, were distinguished for each species. 4. A modified analytical method of isoelectric focusing in polyacrylamide gel indicated a high degree of homogeneity of the purified β and γ isoenzymes from each species, and this was supported by their constant high specific activities. 5. Gel filtration of the isoenzymes in a calibrated column of Sephadex G-100 showed that each had a molecular weight of 45000. 6. Human cathepsin D had a pH optimum of 3.5, and that of chicken enzyme was 3.0, haemoglobin being used as substrate. In each species, the three isoenzymes have the same pH-dependence curve. 7. The purified cathepsin D samples showed very little action on acid-denatured albumin.
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Research Article| April 01 1970
Cathepsin D. Purification of isoenzymes from human and chicken liver
Biochem J (1970) 117 (3): 601–607.
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A. J. Barrett; Cathepsin D. Purification of isoenzymes from human and chicken liver. Biochem J 1 April 1970; 117 (3): 601–607. doi: https://doi.org/10.1042/bj1170601
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