Differences in phosphorylation of phosphoglucomutase 1 in beef steaks from the longissimus dorsi with high or low star probe values.

The objective of this study was to use proteomics to identify alterations of proteins that are related to tenderness. The longissimus dorsi (LD) were removed from ten beef carcasses at 24 h postmortem, and the two with the highest (HSP; average kg of force=6.57) and lowest star probe values (LSP; average kg of force=3.75) at 14 days postmortem were identified. Two-dimensional PAGE was used to compare the sarcoplasmic fraction of the LD from HSP and LSP steaks. A series of spots identified as phosphoglucomutase 1 (PGM1) were identified. Only the most alkaline isoform was identified as being unphosphorylated. The least phosphorylated isoform (isoform 5) had a greater density of the total protein (P<0.05) and phosphorylated protein (P<0.05) in the samples from HSP steaks compared to the samples from LSP steaks. This study illustrates the importance of identifying posttranslational modifications of proteins in the search for biomarkers.