Stability of Proteasomes Extracted from Pressurized, Aged Skeletal Muscles

Abstract

The present paper describes the effects of pressure and post-mortem aging treatments on in situ proteasome activity in rabbit and bovine skeletal muscles. Synthetic peptide hydrolyzing activity of rabbit proteasomes remained in the muscle after exposure to pressures up to 100 MPa. However, when a pressure of 400 MPa or more was applied, proteasomes were markedly inactivated. The extraction of proteasomes from excessively pressurized muscle appeared to be difficult. Proteasomes in aged muscle remained relatively stable throughout the aging process, with activity after 168 h (7 days) being 35%, 48%, 53% and 31% of the 0 h post-mortem LLVY, LSTR, AAF and LLE total hydrolyzing activities, respectively. The synthetic peptide hydrolyzing activities of bovine muscle proteasomes were similar to those of rabbit skeletal muscle proteasomes. The results suggest that synthetic peptide hydrolyzing activity remains in muscle exposed to relatively low pressures. Furthermore, it is known that high-pressure treatment induces fragmentation of myofibrils, modification of actin-myosin interaction and activation of intramuscular proteinases, cathepsins and calpains. Thus, proteasomes are probably involved in the tenderization process in combination with other intramuscular proteinases under high-pressure conditions. Our findings confirmed that proteasomes play a role in meat tenderization induced by high-pressure treatment or aging.