The Effect Of Mitochondrial Apoptosis Mediated By Caspase-3 On Protein Degradation Of Esox Lucius

Fish texture is an important quality index affecting consumer preference and acceptance.Fish softening is a complex biochemical process that inevitably occurs in the preservation of freshwater fish in postslaughter,resulting in the deterioration of texture and flavor.In recent years,apoptosis has been considered to significantly regulate muscle biochemical changes,continuously studied and applied to explain the mechanism of post-mortem fish softening.At present,the research on the effect of apoptosis on muscle quality mainly focuses on the field of livestock,but there is insufficient research on the activation mechanism of mitochondrial apoptotic pathway in the process of post-mortem fish softening.In this study,Esox Lucius were selected as the research objects,and the dorsal muscles were selected as the test samples.The postmortem fish meat was treated with apoptosis inhibitors and inducers to study the effects and changes of apoptosis cascades in mitochondrial apoptosis pathway mediated by caspase-3,and its possible effects on mitochondrial dysfunction.The effect of mitochondrial apoptosis pathway on myofibrillar protein degradation of Esox Lucius was determined during postmortem storage.Improving the theory of softening cell apoptosis of postmortem fish,to provide a theoretical basis for improving postmortem protein degradation of fish and make full use of Xinjiang characteristic cold-water fish.The main results are as follows:1.The effect of caspase-3 inhibitor in mitochondrial apoptosis activation on the degradation of cytoskeleton protein was investigated during postmortem storage.Caspase-3 inhibitor can significantly inhibit the mitochondrial apoptosis cascade,hinder mitochondrial dysfunction,mitochondrial membrane destruction,the release of apoptotic protein(cytochrome c)and the activation of caspase.Through this apoptotic process,it was also observed that apoptosis induced the release of cytochrome c from mitochondria to cytoplasm,which occurred in the early stage of storage.The release of cytochrome c is of great significance in regulating mitochondrial apoptotic pathways during postmortem storage of fish.In addition,mitochondrial apoptosis-mediated fish softening is involved in the degradation of myofibrillar structural protein during postmortem storage.The degradation of small proteins such as desmin and troponin-T may lead to the deterioration of fish texture in the early stage of postmortem storage.While the degradation of large proteins such as titin and nebulin may lead to the further softening of fish texture.Apoptosis in protein degradation is the mechanism of fish softening.Mitochondria play an important role in mediating the mitochondrial apoptosis pathway of texture decline during post-mortem storage.2.Proteins induced by hydroxyl radical oxidation system,with the extension of storage time,the protein structure is destroyed,resulting in the increase of tryptophan fluorescence intensity and secondary structureα-Spiral decreased(P<0.05).Moderate oxidation enhances the sensitivity of caspase-3 to the degradation of myofibrillar protein,intensifies the cross-linking of myosin heavy chain and actin,and produces degradation products.In addition,myosin and troponin-T are degraded to varying degrees.Hydroxyl radicals can change the sensitivity of myofibrillar protein and enhance the hydrolysis of myofibrillar protein by caspase-3.3.The effect of reactive oxygen species(ROS)-mediated the activation of mitochondrial apoptosis on cytoskeleton protein degradation during postmortem storage.ROS-induced oxidation accelerated mitochondrial oxidative stress,resulting in the decrease of antioxidant enzyme activities(CAT,SOD,and GSH-PX)and the increase of MDA concentration(P<0.05).ROS-mediated oxidative stress increased MPTP opening,mitochondrial membrane swelling and membrane potential collapse during postmortem storage.The enhanced production and translocation of cytochrome c in oxidized fish muscle also induced caspase-3activation through initiating mitochondrial apoptosis pathway.In addition,oxidation leads to the degradation of small proteins but inhibits the degradation of large proteins.This is because oxidation causes changes in myofibrils,resulting in different sensitivity to protein hydrolysis.Oxidative stress activates mitochondrial apoptosis,participates in regulating the changes of apoptotic factors in fish muscle,and contributes to the proteolysis of cytoskeletal proteins.