Action of Proteolytic Enzymes on Bovine Myofibrils

Abstract

The effect of cathepsin D from muscle and spleen on bovine myofibrils has been examined under postmortem pH conditions using sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, scanning electron microscopy (SEM) and electron spin resonance spectroscopy (ESR). Cathepsin D causes a degradaticy of 2 disks of the myofibrils and has a relatively selective action on the myofibrillar proteins in comparison to the plant derived enzyme papain. The heavy chain of myosin (200,000 daltons) was degraded to fragments of about 170,000, 150,000, and 80,000 daltons at 25°C. Degradation becomes more extensive at 37°C. ESR studies on spin-labeled myofibrils indicated that the proteolytic attack of cathepsin D occurred more distal to the globular region of the myosin when compared to papain or trypsin. Although there appears to be little proteolytic effect on o-actinin or actin, changes in the gel electrophoresis pattern below 42,000 daltons indicate alterations of the regulatory complex and myosin light chains.

Cathepsin D and Its Effects on Myofibrillar Proteins: A Review

“…The degradation of myosin heavy chain as a result of the action of cathepsin D produced two major groups of fragments with molecular weights of approximately 120,000 and 90,000. The latter fragments are of sufficient size to be myosin S-1 fragments as proposed in several investigations (Robbins et al 1979;Yates et al 1983;Elgasim et al 1985). It would be of interest to know which regions of the myosin molecule were attacked by cathepsin D and how the enzyme might participate in disassembly of the thick filament but these questions will have to be addressed in future research.…”

Role of Muscle Proteinases in Maintenance of Muscle Integrity and Mass

“…Indeed, among the known proteolytic enzymes, CAF is unique in its inability to degrade myosin (Table 3). Together, these basic experimental findings inculpate CAF as the agent responsible for most postmortem proteolysis of myofibrillar proteins, even though cathepsins L (Matsukura et al 1981) and D both can produce 3OKdalton polypeptide fragments when incubated with troponin or myofibrils, and cathepsin D can degrade Z-disks in myofibrils at pH 5.2 to 5.3 (Robbins et al 1979).…”

Tenderization of Spent Hen Muscle Using Papain, Bromelin, or Ficin Alone and in Combination with Salts

“…These collagens were shown to be resistant to the action of papain, trypsin, and chymo trypsin. Robbins et al (1979) used SDS (sodium dodecyl sulphate) gel electrophoresis to show the effect of papain on bovine myofibrils.…”

“…Actomyosin was less rapidly digested than the myosin. Robbins et al (1979) showed that cathepsin-D extracted from muscle or spleen degraded myofibrils under postmortem pH conditions (5.1-5.3)…”

“…Rattrie and Regenstein (1977) showed that the selective action of cathepsin-D on the myosin component of myofibrils was in contrast to the breakdown of that protein which would occur when myofibrils were incubated with trypsin or papain. Robbins et al (1979) pointed out that due to the selectivity of cathepsin-D towards the proteins of the myofibrils, it could be used as an exogenous meat tenderizer and that the texture of muscle treated with cathepsin-D was similar to that of naturally aged muscles in contrast to the "mush" texture resulting from indiscriminate degradation of the myofibrillar proteins by commercial tender izers containing papain.…”