Tandem Mass Tag Labeling–Based Analysis to Characterize Muscle-Specific Proteome Changes During Postmortem Aging of Bison Longissimus Lumborum and Psoas Major Muscles

The objective of the study was to examine the variations in sarcoplasmic proteomes of bison longissimus lum-borum (LL) and psoas major (PM) muscles during postmortem aging utilizing tandem mass tag isobaric labeling coupled with liquid chromatography–mass spectrometry for the categorization of muscles with muscle-specific inherent color sta-bility. A total of 576 proteins were identified in both bison LL and PM muscles, where 97 proteins were identified as differ-entially abundant (fold change > 1.5, P < 0.05) from the 3 comparisons between muscles during postmortem aging periods (PM vs. LL at 2 d, 7 d, and 14 d). Between muscles, the most abundant protein groups were based on functions such as electron transport chain or oxidative phosphorylation, tricarboxylic acid cycle, adenosine triphosphate transport, carbohydrate metabolism, fatty acid oxidation, chaperones, oxygen transport, muscle contraction, calcium signaling, and protein synthesis. In PM, most of the proteins from electron transport chain, tricarboxylic acid cycle, fatty acid oxidation, adenosine triphosphate and oxygen transport, and muscle contraction were more abundant or exhibited increased expression during aging compared with LL. On the other hand, the proteins involved in carbohydrate metabolism, chaperone function, and protein synthesis mostly exhibited decreased expression in PM muscles relative to LL. These results clearly demonstrate that the proteins associated with oxidative metabolism showed increased expression in PM muscles. This indicates that oxidative damage and subsequent color deterioration resulted in bison PM muscles being attacked by the reactive oxygen species produced during those metabolic processes. In contrast, proteins involved in glycolysis and chaperone activity exhibited a decrease in expression in bison PM muscles, resulting in a decline in color stability compared with LL. Because glycolytic enzymes generate reducing equivalents and chaperones maintain the native folded protein structure, they are consequently responsible for the color stability in LL muscles compared with PM.