Quantitative N-Glycoproteomic Analysis of Cattle-Yak and Yak Longissimus Thoracis

In this study, the N-glycosylated protein profiles of cattle-yak longissimus thoracis (CYLT) and yak longissimus thoracis (YLT) were comparatively analyzed using quantitative proteomics techniques. A total of 76 differential N-glycosylated proteins (DGPs) were screened from 181 quantified N-glycoproteins, indicating that differences in N-glycosylation levels are key to the differences between CYLT and YLT. In particular, a variety of N-glycoproteins involved in the extracellular matrix were differentially N-glycosylated between CYLT and YLT, mainly including fibrillin-1, fibromodulin, collagen, and laminins. In addition, the N-glycosylation levels of several lysosomal-related proteolytic enzymes (cathepsin D, dipeptidyl peptidase 1, legumain, and aminopeptidases, etc.) were significantly higher in CYLT. These results indicated that the N-glycosylation of CYLT and YLT proteins plays a crucial role in the regulation of extracellular matrix organization (muscle fiber structure) and lysosomal activity (postmortem meat tenderness). The results remind us that posttranslation modifications, especially N-glycosylation, are still icebergs beneath the surface.