The isolation and properties of a proteolytic enzyme, cathepsin D, from bovine spleen

Abstract

HAEM-PROTEIN REDUCTION BY COLOROPLASTS 501 to the conclusion that the factor can catalyse the reduction of soluble material in the leaf extracts. Further work is necessary to trace the paths of hydrogen transport after the reduction of the factor by the illuminated chloroplast and to determine the nature of the group concerned in the oxidation-reduction cycle. SUMMARY 1. A protein factor from leaves, previously shown to be active in catalysing the reduction of methaemoglobin and metmyoglobin by illuminated chloroplasts, has been purified by fractionation with ammonium sulphate followed by electrophoretic separation of the active material on paper. 2. The purified protein was found to give a single symmetrical boundary in the ultracentrifuge and in the Tiselius electrophoresis apparatus. 3. The molecular weight of the protein, calculated from sedimentation and diffusion measurements, is 19 000. 4. The purified protein is highly active in catalysing the photochemical reduction of metmyoglobin and also stimulates the reduction of cytochrome c, cytochrome b3 and the cytochrome components present in a particulate heart-muscle preparation. 5. The photochemical reduction is inhibited by organic mercury compounds and this inhibition is partially reversed by cysteine. 6. The protein does not catalyse the reduction of haem-proteins when coenzymes served as hydrogen donor. Illuminated chloroplasts were the only effective hydrogen-donating system observed. 7. The chemical nature of the group conferring oxidation-reduction properties to the protein has not yet been determined but neither flavin nor haem could be detected. 8. Metmyoglobin-reducing activity has been observed in extracts of chloroplasts and was shown to represent one-third of the activity extractable from the whole leaf. In addition to the acknowledgements made in the text the authors wish to acknowledge the help of Mr F. W. Arnold and the late Mr H. Pentelow in the collection of leaf material, and to thank Mr B. E. Boon for his assistance with the ultracentrifuge runs and Mr B. R. Slater for the diffusion measurements. This work formed part of a programme supported by the Agricultural Research Council.

Cathepsin E (EC 3.4.23.34) — a review

“…Yet, albumin is a substrate more specific for cathepsin E, and globin for cathepsin D [62][63][64] (Table 8). Figure 9.…”

Neutral proteinases of human spleen. Purification and criteria for homogeneity of elastase and cathepsin G

“…The major acid proteinase, now called cathepsin D, was studied by Anson (1939) and other acid peptidases of the bovine spleen were characterized by Fruton and coworkers (Tallan et al, 1952). The interest of immunologists in the processing ofprotein immunogens in the spleen led to further work on cathepsin D (Lapresle & Webb, 1960;Press et al, 1960), and also to the studies of Zff and co-workers LoSpalluto et al, 1970) on the degradation of immunoglobulins by human spleen enzymes at both acid and neutral pH values. The purpose of the present study was to purify and characterize the enzymes responsible for the neutral proteinase activity of human spleen.…”

Action of proteolytic enzymes on lipotropins and endorphins: Biosynthesis, biotransformation and fate

“…In contrast to above mentioned studies seven to eight cleavage sites in porcine //-lipotropin have been reported by Akopyan and colleagues who used a cathepsin D Barfit et al (1979), the data have been reconsidered in view of the revised human fl-lipotropin structure (see Fig. 2); (C) Gr~f et al (1979b), Benuck et al (1978b), Burbach et al (1980b); (D) Lebouille and Burbach (unpublished); (E) Press et al (1960).…”