Protein Acetylation At Lysine ε-Amino Regulates Postmortem Muscle Glycolysis

Pale、Soft、Exudative meat brought huge economic losses on the slaughter and meat processing industry because of its low quality.This problem aroused people’s great attention from the 80 s of last century,but has not been completely resolved.The fundamental reason is that its molecular mechanism is unclearly.A large number of studies have shown that rapid postmortem glycolysis reduce the pH and increase the temperature of muscle which make the muscle protein denatured.This is the root cause of PSE meat.However,the regulation of postmortem muscle glycolysis is still unknown and how does pre-slaughter stress affect postprandial muscle glycolysis and the quality,color,tenderness and other food quality of meat is still unknown too.Its signal transduction process and molecular mechanism remains to be studied.Many studies on the activity of the glycolytic enzyme in the postmortem muscle indicate that the glycolysis in the postmortem muscle may have a different mechanism or a unrevealed new mechanism that is different with living animals.In order to explore these mechanisms,and confirm the regulation role of protein acetylation on muscle glycogenysis we inject acetylationase(HAT)and deacetylase(HDAC)to mice.The changes of acetyl protein mass spectrum in skeletal muscle of porcine were studied by quantitative acetylation protein mass spectrometry and the impact of pre-slack transport and rest on pork quality was analyzed also.we provide new information by the further study of acetylation of protein and the molecular mechanism of protein acetylation in postprandial muscle glycolysis and meat quality.The main conclusions are as follows:1.HAT inhibitor(HAT inhibitor Ⅱ)antagonizes the promoting effect of AMPK on glycolysis and reducing the level of protein acetylation in mouse muscle.In contrast to HAT inhibitors,intraperitoneal injection of HDAC inhibitors TSA and NAM significantly increased the acetylation level and glycolytic rate of protein in muscle at 45 min after slaughter,and it also reduced muscle pH and increased lactate content.These results suggest that protein acetylation plays an important role in mediator muscle glycolysis and mediates AMPK’s regulation of postprandial glycolysis.2.Pre-slaughter transport accelerate the decrease of glycolysis and pH value in slaughter pigs,reduce the water retention,tenderness,color and other qualities of pork,while an appropriate rest after transportation partly eliminate the adverse effects of pre-slaughter stress on pork quality and the meat quality has a significant improvement.3.595 specific acetylated peptides,598 protein acetylation sites and 171 acetylated proteins were identified by Acetyl Protein Mass Spectrometry from the postpartum pig longissimus dorsi muscle.Most of these proteins are monoacetylated proteins.Among them,myosin heavy chain(MHC)-based proteins were the highest levels of acetylation.70,35 and 26 acetylation sites were detected in MHC IId / x,MHCβ and MHCⅡb,respectively.Bioinformatics analysis showed that these acetylated porcine muscle proteins were mainly membrane proteins,cytoplasmic proteins and mitochondrial proteins.The molecular functional classification were mainly metal ion binding and DNA binding proteins.The biological processes classification were mainly carbohydrates,glucose metabolism,signal transduction and transport proteins.A total of 5 lysine ε-aminoacetylated motifs ExxxK,QxxxxK,EK,KxxxxxK and ExxxxK were identified by Acetylated pH enotypic Analysis from the identified acetylation sites.4.Quantitative analysis showed that the acetylation of protein in skeletal muscle of postpartum pigs was a dynamic process.The level of acetylation of muscle protein in pigs was generally decreased within 24 hours after slaughter.However,the overall acetylation level of the protein at 0 to 4 hours after slaughter has an up regulation process.That may indicate the end of stress response,ATP depletion,and the beginning of the transformation process.Protein interaction analysis showed that the proteins modified in the muscle of the postpartum pig were mainly energy metabolism and muscle structural protein.It is suggested that the acetylation of protein may play an important role in the regulation of muscle saccharification,glycogen degradation,muscle contraction and zygote.Validate the function of these acetylated proteins is a research direction in the future.