Study On The Mechanism Of Peroxiredoxin 6 Regulating Beef Color Based On Oxidative Stress Pathway

Meat color is one of the important edible qualities of beef.Maintaining meat color and its stability has always been a focus of meat science research.After slaughter,the hypoxia-ischemia environment leads to the continuous accumulation of reactive oxygen species（ROS）in the meat,which causing oxidative stress and ultimately affecting the browning process of beef color.Peroxidase 6（Prdx6）is a key antioxidant enzyme in beef that plays an important role in maintaining the body’s redox homeostasis and protecting the body from oxidative stress damage,ultimately affecting meat color and its stability.Previous studies have shown that Prdx6 is a biomarker which affects the beef color and its stability during postmortem aging.However,the specific mechanism of Prdx6 and its non-selenium glutathione peroxidase（NSGPx）activity regulating meat color has not been reported.In this study,simmental crossbred cattle were selected as experimental samples,which were cut and soaked separately in N-acetyl-L-cysteine solution（NAC,inhibiting oxidative stress treatment group）,mercaptosuccinic acid solution（MA,inhibiting Prdx6 NSGPx activity treatment group）,hydrogen peroxide solution（H₂O₂,enhancing oxidative stress treatment group）,and physiological saline as a control.The study determined the effect of Prdx6 NSGPx activity on beef color formation by measuring Prdx6 NSGPx activity and meat color indicators.Furtherly explored the regulatory mechanism of Prdx6 NSGPx activity on beef color formation from the aspects of oxidative damage to fats and proteins and mitochondrial dysfunction by measuring indicators such as thiobarbituric acid reactive substances（TBARS）,protein carbonyl content,mitochondrial membrane permeability,and nicotinamide adenine dinucleotide（NADH）content.Proteomics analysis was also used to reveal the potential mechanism by which Prdx6NSGPx activity regulates beef color and its stability,in order to improve the understanding of the formation mechanism of beef color.The main results of this study are as follows:（1）Inhibiting Prdx6 NSGPx activity can accelerate the meat discoloration after slaughter.During the postmortem aging,MA treatment significantly increased oxidative stress by inhibiting Prdx6 NSGPx activity in the beef samples,and accelerated the meat discoloration;H₂O₂ treatment significantly increased oxidative stress,and oxidative stress initially increased Prdx6 NSGPx activity and then decreased it.The increased adaptability of Prdx6 NSGPx activity was beneficial for maintaining meat color in the early stages after slaughter,but H₂O₂treatment ultimately accelerated the meat discoloration.The results of the study showed that both inhibiting Prdx6 NSGPx activity and enhancing oxidative stress treatment could accelerate the meat discoloration for which increased oxidative stress,and the inhibiting Prdx6 NSGPx activity treatment had a more significant effect on the meat discoloration.（2）Inhibiting Prdx6 NSGPx activity regulated beef color by increasing the degree of oxidation of fats and proteins,at the same time,damaging mitochondrial function.Both MA treatment and H₂O₂ treatment increased the content of malondialdehyde（MDA）,protein carbonyl content,and surface hydrophobicity in the beef samples,these indicated that inhibiting Prdx6 NSGPx activity and enhancing oxidative stress treatment increased the degree of oxidation of fats and proteins,and the inhibiting Prdx6 NSGPx activity treatment had a greater effect in the early postmortem period（24 hours after slaughter）.Both MA treatment and H₂O₂treatment increased the opening degree of the membrane permeability transport pore（MPTP）in the beef samples,and reduced the metmyoglobin reducing activity（MRA）,oxygen consumption rate（OCR）,and NADH content,indicating that inhibiting Prdx6 NSGPx activity and enhancing oxidative stress treatment aggravated the degree of mitochondrial oxidative damage and led to mitochondrial dysfunction.Therefore,inhibiting Prdx6 NSGPx activity and enhancing oxidative stress treatment affected the oxidation-reduction of myoglobin by promoting processes such as fat oxidation,protein oxidation,and mitochondrial dysfunction,thereby accelerating meat discoloration.（3）Proteomics analysis showed that inhibiting Prdx6 NSGPx activity affected the expression of proteins related to amino acid metabolism,glycolysis,and the tricarboxylic acid cycle in beef in the early postmortem period.It hindered the reduction of metmyoglobin by mitochondria through affecting the production of NADH and the process of mitochondrial respiratory electron transfer chain,ultimately having an adverse effect on the formation of beef color in the early postmortem period.Among them,changes in the expression of proteins such as acyl-coenzyme A oxidase（ACOXL）,cytochrome c oxidase subunit 7A1（COX7A1）,2-oxoisovalerate dehydrogenase subunit beta,mitochondrial（BCKDHB）,and 2-phospho-D-glycerate hydro-lyase（ENO2）may be potential markers of oxidative stress and further affect meat color.