Studies on lysosomes in rat heart cell cultures. II. The effect of exogenous lysosomes

Friedman, I.; Laufer, A.; Davies, A.M.

doi:10.1007/bf01901451

Cited by 7 publications

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“…In the biochemical analyses of Park & Pennington (1967) and Bodwell & Pearson (1964) only proteolysis products soluble in trichloroacetic acid were measured, which would not include relatively large polypeptide fragments detectable in SDS/polyacrylamide gels. The techniques used by Sharpe (1963) and Friedman et al (1969) did not provide the resolution necessary to detect changes in myofibrillar structure. Martins & Whitaker (1968) and Fukazawa & Yasui (1967) used incubation temperatures (4 and 0°C respectively) at which the cathepsins have little or no activity.…”

Section: Discussionmentioning

confidence: 99%

Degradation of myofibrillar proteins by cathepsins B and D

Schwartz

Bird

1977

Biochemical Journal

264

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1. The procedure of Barrett [(1973) Biochem. J.131, 809-822] for isolating cathepsins B and D from human liver was modified for use with rat liver and skeletal muscle. The purified enzymes appeared to be similar to those reported in other species. 2. Sephadex G-75 chromatography of concentrated muscle extract resolved two peaks of cathepsin B inhibitory activity, corresponding to molecular weights of 12500 and 62000. 3. The degradation of purified myofibrillar proteins by cathepsins B and D was clearly demonstrated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. After incubation with enzyme, the polypeptide bands representing the substrates decreased in intensity and lower molecular weight products appeared. 4. Cathepsins B and D, purified from either rat liver or skeletal muscle, were shown to degrade myosin, purified from either rabbit or rat muscle. Soluble denatured myosin was degraded more extensively than insoluble native myosin. Degradation by cathepsin B was inhibited by lack of reducing agent, or by myoglobin, iodoacetic acid and leupeptin, but not by pepstatin. The same potential modifiers were applied to cathepsin D, and only pepstatin produced inhibition. 5. Rat liver cathepsin B had a pH optimum of 5.2 on native rabbit myosin. The pH optimum of cathepsin D was 4.0, with a shoulder of activity about 1pH unit above the optimum. 6. Rat liver cathepsins B and D were demonstrated to degrade rabbit F-actin at pH5.0, and were inhibited by leupeptin and pepstain, respectively. 7. The degradation of myosin and actin by cathepsin D was more extensive than that by cathepsin B.

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