Effects of age and tissue type on the calpain proteolytic system in turkey skeletal muscle

Calpain activation and proteolysis in postmortem goose muscles

Meat tenderness is considered as the most important criterion for meat quality by consumers and can be improved by the actions of endogenous proteases, mainly calpains, during postmortem storage at 0-5°C. The purpose of this study, therefore, was to examine the postmortem calpain activation and proteolysis in breast (BM) and leg and thigh (LM) muscles of White Roman goose. BM and LM were taken from goose carcasses (n = 15) at 0 (10-15 min postmortem), 1, 3, and 7 days of storage at 5°C. The decrease in postmortem pH, calpain-1 and -11 activities, and contents of the calpain-1 80 kDa subunit and desmin was more rapid (p < .05) in BM than in LM. Our results show that postmortem proteolysis was more extensive in BM than in LM of White Roman goose, not only because the difference in fiber type composition between two muscles, but because the rate and extent of calpain activation were greater in BM as well. These results may provide useful information to optimize meat processing for different muscles in goose industry.

Postmortem proteolysis in three muscles from growing and mature beef cattle

The objective of this study was to determine calpain system activity and postmortem protein degradation in three muscles from growing (n=6, 7.3 ± 0.5 months) and mature (n=6, 106.7 ± 43.1 months) beef cattle. The ratio of μ-calpain:total calpastatin activity tended to be lower in mature animals (P=0.08), suggesting reduced potential for proteolysis. Additionally, muscles from the mature group had greater calpastatin activity compared to calves at 6 days postmortem and had less μ-calpain autolysis and troponin-T and titin degradation during the aging period (P<0.01). Between the longissimus, semimembranosus, and triceps brachii muscles, the triceps brachii had the least postmortem proteolysis, with greater calpastatin activity and less troponin-T and titin degradation compared to other muscles (P<0.01). These data suggest that calpastatin activity in muscle from older animals is more persistent postmortem. This difference may contribute to the decreased protein degradation and increased toughness of beef from mature cattle, even after aging.

Effect of processing on turkey meat quality and proteolysis

Modern processing techniques for turkey involve rapid chilling to slow microbial growth and early deboning of the economically important breast meat. This paper shows that these 2 processes lead to significantly tougher meat with higher cooking losses. The toughening appears to be due to less extensive proteolysis and shortening of the sarcomeres. Calpains I and II and their inhibitor, calpastatin, were quantified in turkey breast. Calpain II was the more common isoform but showed no evidence of activation during aging. In contrast, calpain I and calpastatin activities declined rapidly and were no longer detected 24 h postslaughter. There was no evidence of an association between calpain activity and processing conditions.

Adverse and beneficial functions of proteolytic enzymes in skeletal muscle. An overview

Proteolytic enzymes (proteases) comprise a family of enzymes which hydrolyse protein or peptide substrates in the generalised process of intracellular protein degradation, a process essential for the normal functioning of all cells. Proteases may also have a wide range of additional functions, including metabolic control of physiologically active oligopeptides or precursor protein forms, antigen presentation/recognition by the major histocompatibility complex in the cellular immune response, as well as in digestion, blood clotting, complement activation, etc. In this article, the nomenclature and classification of proteolytic enzymes in skeletal muscle, and their role in normal muscle physiological processes have been reviewed, including exercise, muscle development and ageing. Although proteases play an important role in normal muscle functioning, in pathological situations the enzymes may themselves be regarded as 'toxic agents' in terms of their damaging effects on muscle tissue. Muscle damage resulting from inappropriate activity of proteolytic enzymes in muscle wasting associated with muscular dystrophies, denervation atrophy, inflammatory myopathies, cancer, sepsis, diabetes and alcoholism have been reviewed. In addition, evidence that the adverse effects of drugs known to induce muscle wasting, such as corticosteroids, (or beneficial effects of growth promoting drugs) may be mediated via proteolytic enzymes is also reviewed.

The effect of early posthatch starvation on calpain mRNA levels

The calpain system is a family of calcium activated proteases that degrade myofibrillar protein. Male broiler chickens (Ross) were provided a standard starter diet top-dressed with Oasis((R)) nutritional supplement (fed; Novus International, St. Louis, MO, USA), or they were not provided any feed (starved) for the first 3 days posthatch. Subsequently, the standard starter diet was provided to all chickens between 3 and 7 days posthatch. RNA was extracted from the Pectoralis thoracicus, and skeletal muscle-specific n-calpain-1 (p94) calpain, mu-calpain, and m-calpain expression was evaluated using quantitative Northern analysis. Early posthatch starvation did not (P>0.05) affect calpain mRNA levels on each day examined. Similarly, there were no (P>0.05) changes in mu-calpain or m-calpain mRNA levels between 0 and 7 days posthatch in fed birds. However, p94 calpain mRNA levels were significantly (P<0.05) lower at 7 days posthatch compared to 0 or 2 days posthatch. Therefore, in the early posthatch chicken, it appears that the calpain system may not be affected by the presence of oral nutrition, and that there is an age-related downregulation of p94 calpain mRNA expression.

Influence of preslaughter stunning on turkey breast muscle quality

Pectoralis muscle quality was evaluated from 18-wk-old tom turkeys after electrical stun, carbon dioxide stun, or no stun methods were applied. Color was measured on raw muscle and cooked meat using a colorimeter. Muscle pH was measured 15 min post-mortem (initial), 24 h post-mortem (final), and after cooking. The right Pectoralis muscle of each carcass was excised for m-calpain analysis within 4 min post-mortem. After 24 h of storage at 4 C, the left Pectoralis muscle was excised to determine cook loss and shear force measurements. No significant difference was found in initial muscle pH (15 min) from turkeys receiving electrical or carbon dioxide stunning, 6.36+/-0.15 and 6.20+/-0.14, respectively. However, initial muscle pH for birds that were not stunned (5.99+/-0.08) was lower (P < 0.05) than the muscle pH of birds stunned using either of the two stunning methods. Stunning method had no effect on the final muscle pH, raw muscle color, cooked meat pH, cooked meat color, cook loss, or shear force. Cook loss was found to positively correlate with initial muscle lightness (r = 0.53), and cooked meat lightness (r = 0.48), but to negatively correlate with cooked meat yellowness (r = -0.48) and shear strength (r = -0.43). m-Calpain activity declined with the stunning methods in the following order: electrical > carbon dioxide > no stun. In addition, m-calpain activity was found to correlate with initial muscle pH (r = 0.95) and with cooked meat shear force (r = -0.43). The results of this study show that electrical stunning, carbon dioxide stunning, and no stunning methods provide comparable cooked turkey breast meat quality with no consistent differences after aging on the carcass for 24 h.