Protein phosphorylation can regulate most of the important processes in muscle, such as metabolism and contraction. The postmortem (PM) metabolism and
rigor mortis have essential effects on meat quality. In order to identify and characterize the
protein phosphorylation events involved in meat quality development, a quantitative mass spectrometry-based phosphoproteomic study was performed to analyze the porcine muscle within 24h PM using dimethyl labeling combined with the TiSH
phosphopeptide enrichment strategy. In total 305 unique
proteins were identified, including 160
phosphoproteins with 784 phosphorylation sites. Among these, 184 phosphorylation sites on 93
proteins had their phosphorylation levels significantly changed. The
proteins involved in
glucose metabolism and muscle contraction were the two largest clusters of
phosphoproteins with significantly changed phosphorylation levels in muscle within 24 h PM. The high phosphorylation level of
heat shock proteins (HSPs) in early PM may be an adaptive response to slaughter stress and protect muscle cell from apoptosis, as observed in the
serine 84 of HSP27. This work indicated that PM
muscle proteins underwent significant changes at the phosphorylation level but were relatively stable at the total
protein level, suggesting that
protein phosphorylation may have important roles in meat quality development through the regulation of
proteins involved in
glucose metabolism and muscle contraction, thereby affecting glycolysis and
rigor mortis development in PM muscle.
BIOLOGICAL SIGNIFICANCE: The manuscript describes the characterization of postmortem (PM) porcine muscle within 24 h postmortem from the perspective of
protein phosphorylation using advanced phosphoproteomic techniques. In the study, the authors employed the dimethyl labeling combined with the TiSH
phosphopeptide enrichment and LC-MS/MS strategy. This was the first high-throughput quantitative phosphoproteomic study in PM muscle of farm animals. In the work, both the
proteome and phosphoproteome were analyzed, and the large number of identified
peptides,
phosphopeptides and phosphorylation sites can greatly enrich the current farm animal protein database. The
proteins involved in glycometabolism, muscle contraction and
heat shock proteins (HSPs) showed significantly changed phosphorylation levels during PM meat development. This work indicated that PM
muscle proteins underwent significant changes at phosphorylation level but were relatively stable at the total
protein level, suggesting that
protein phosphorylation may have important roles in meat development through the regulation of
proteins involved in metabolism and muscle contraction, thereby affecting glycolysis and
rigor mortis development in PM muscle. The work can promote the understanding of PM muscle metabolism and meat quality development, and be helpful for future meat quality control.