Mechanisms Of Post-slaughter Meat Quality Changes In Response To Proteasome Activity In Qinchuan Beef

Proteasomes play an important role in meat quality indicators.Although proteasome and postslaughter muscle tenderisation have been studied in depth,there is still a lack of research on the relationship between proteasome and other muscle qualities and the effects of the UPP mediated by proteasome on meat quality.In this study,the longissimus dorsi muscle of Qinchuan cattle stored at 4℃after slaughter was used as the object of study to determine quality indicators,energy levels and proteasome activity,and to identify DEPs associated with the proteasome.The proteasomal response to post-slaughter beef quality and energy metabolism was analysed using bioinformatics,and the proteasomal-mediated UPP pathway was investigated by injecting the proteasome inhibitor MG-132 on the storage of post-slaughter Qinchuan beef to provide theoretical support for the precise regulation of post-slaughter beef quality.The main findings were as follows:1.Proteasome activity and energy levels during post-slaughter storage and their relationship with meat quality were analysed.The pH value decreased and then increased with increasing storage time;b*value and MFI increased;L*value,a*value,centrifugal loss,cooking loss and shear force increased and then decreased;ATP,ADP and AMP,the basic substances of energy,decreased;20S proteasome activity decreased significantly(P<0.05).The correlation analysis showed that 20S proteasome activity was significantly negatively correlated with b*value(P<0.05),ADP content(P<0.05),AMP content(P<0.01)and MFI(P<0.01).The above findings suggest that there is a close relationship between proteasome activity and beef energy metabolism and quality during storage in the longest back muscle of post-slaughter Qinchuan cattle.2.The potential mechanism of proteasome regulation of meat quality during post-slaughter storage was initially revealed.Identification of eight differentially expressed proteasomal subunits based on 4DLFQ proteomics technology,and correlated with the expression of the screened DEPs,combined with String for PPI interaction analysis,and finally screened 27 related DEPs;GO analysis and KEGG Pathway analysis revealed that these proteasomal subunits GO analysis and KEGG Pathway analysis revealed that these proteasome subunits and their associated DEPs had molecular functions such as endopeptidase activity,actin binding and microfilament motility,and were involved in ubiquitindependent proteolytic metabolism,skeletal muscle contraction,muscle contraction,glycolysis and other biological processes,causing changes in the quality of Qinchuan beef.At the beginning of the postslaughter period,the proteasome regulates the biological pathway by consuming energy,and at the end of the post-slaughter period,the proteasome can metabolise proteins through glycolysis and non-ATPdependent proteasome subunits,ultimately affecting the quality of Qinchuan beef.3.The effect of proteasome and its mediated UPP pathway on protein degradation after slaughter was clarified.With the extension of storage time,the proteasome activity in the MG-132 group was lower than that in the control group,and the total soluble protein content and ubiquitin protein content were higher than those in the control group;the SDS-PAGE results showed that the total soluble protein bands in the MG-132 group were overall deeper than those in the control group;the longest muscle structure of the bovine back in the MG-132 group was better preserved,and the boundaries of the Z line and the bright and dark bands were clearer than those in the control group;and The total soluble protein and ubiquitin protein content were significantly correlated(P<0.05).In conclusion,MG-132 inhibited proteasome activity and the degradation of ubiquitinated proteins in the UPP pathway in post-mortem Qinchuan beef,which in turn altered the post-mortem protein degradation and reduced the destruction of muscle ultrastructure,indicating that the post-mortem UPP pathway has a potential role in meat formation and that the proteasome,in addition to degrading protein alone and destroying post-mortem myogenic fibre structure,also influences post-mortem protein degradation by mediating the UPP pathway.In addition to degrading protein alone and destroying post-mortem myogenic fibril structure,the proteasome also influences post-mortem beef protein degradation through mediating the UPP pathway,ultimately affecting post-mortem beef quality.