Peroxiredoxin-6--a potential protein marker for meat tenderness in bovine longissimus thoracis muscle.

The muscle sarcoplasmic proteins from bovine M. longissimus thoracis muscle were studied using proteomics to identify possible protein markers for meat tenderness. This study included 3 experiments: A1, A2, and B. From a collection of biopsies from the bovine M. longissimus thoracis muscle, excised 4 d before slaughter from 178 Norwegian Red young bulls, 26 biopsies were studied in Exp. A1. Based on Warner-Bratzler shear force (WBSF) values at 7 d postmortem, the biopsies were separated into a tender and a tough group of 13 bulls each and analyzed by 2-dimensional gel electrophoresis (2-DE) and Western blotting. The 2-DE experiments identified 4 different proteins: stress-70 protein, protein DJ-1, peroxiredoxin-6, and malate dehydrogenase, which were different in abundance in the tender and tough groups. However, only peroxiredoxin-6 was confirmed by quantification from Western blots. Peroxiredoxin-6 is an antioxidant enzyme that plays a role in protecting cells from oxidative stress. Peroxiredoxin-6 was identified through 3 spots of the same molecular weight, but with different pI on the Western blots. Only one of the spots was more abundant in the biopsies from the tender group. In Exp. A2, samples collected 1 h postmortem from the same animals and muscles as in Exp. A1 were analyzed by Western blotting. In these postmortem samples, the same spot from peroxiredoxin-6 as in Exp. A1 was more abundant in the tender group. In addition, one of the other peroxiredoxin-6 spots was also more abundant in the tender group. To verify the results from Exp. A, biopsies from 14 additional animals were analyzed in Exp. B by Western blotting against stress-70 protein, protein DJ-1, peroxiredoxin-6, and malate dehydrogenase. No significant differences between the tough and tender groups could be observed in these biopsies. However, for peroxiredoxin-6, the tendencies pointed in the same direction as in Exp. A. In conclusion, peroxiredoxin-6 might be a potential protein marker for meat tenderness detectable in biopsies and in samples collected shortly after slaughter. However, more animals are needed to verify the findings in the present study.