Early degradation of myosin light chains beneficially impacts human health of sea bream (Sparus aurata) consumers

inglese

This work investigated on the pre-slaughter changes in sea bream muscle proteins as affected by fish pre-slaughter fasting in comparison to full feeding and how these changes could affect the presence of active peptides and the gastric digestibility of sea bream fillet. In the early post-mortem, actin fragments were detected in both the samples regardless of the feeding regime, while only in the fasted fish samples myosin light chains were found markedly degraded in the early post-mortem. On the other hand, degradation was also evident in the full feeding samples, where myosin light chains were no longer visible during post mortem storage at 4 °C, consistent with the natural instability of these fish proteins in comparison to the mammal ones. ACE-inhibitor gastric-resistant bioactive peptides (VF, MF, VAF), which derived from myosin light chains, were found in both the samples, regardless of the feeding regime, with one of these peptides (VF) seeming in larger amount in the fasted samples. By using static standardized in-vitro digestion methods, digestibility of myosin was found to increase to a greater extent in the fasted samples at pH 4.0, when individual test enzymes were applied under conditions of drug-induced high pH occurring in GERD patients. Differences in myosin gastric digestibility were also apparent at pH 3.0, while at this pH actin was found susceptible to full proteolysis, irrespective of the feeding regime. Therefore, it appeared that under conditions which caused an early degradation of the myosin light chain and possibly an impaired myosin integrity, gastric digestibility of the main myofibrillar proteins was much higher in the altered gastric milieu. In conclusion, sea bream feed restriction, other than decreases the environmental impact of fish aquaculture, seems to act on fish proteins, resulting in nutritional benefits for hypertensive and GERD patients.