Early postmortem muscle proteome and metabolome of beef longissimus thoracis muscle classified by pH at 6 hours postmortem.

The objective was to identify metabolome and proteome differences at 1 h and 1 d postmortem between longissimus thoracis (LT) muscle classified based on 6 h pH values. Twenty beef LT rib sections were sorted based on 6 h postmortem pH values into low (LpH; pH < 5.55; n = 9) and high (HpH; pH > 5.84; n = 8) pH classifications. Warner-Bratzler shear force (WBSF), desmin degradation, and calpain-1 autolysis were measured. Two-dimensional difference in gel electrophoresis (3-10, 4-7, and 6-9 pH range) and Tandem mass tagging (TMT) protein analyses were employed to determine how the sarcoplasmic protein profile varied across pH classification. Non-targeted metabolomic analyses were conducted on extracts prepared at 1 h and 1 d postmortem. The LpH classification had a lower WBSF value at 1 d postmortem, which was explained by greater calpain-1 autolysis and desmin degradation at 1 d postmortem. Proteome and metabolome analysis revealed a phenotype that promotes more rapid energy metabolism in the LpH group. Proteome and metabolome analyses identified energy production, apoptotic, calcium homeostasis, and proteasome systems influencing pH classifications that could explain the observed pH, proteolysis, and beef tenderness differences. SIGNIFICANCE: This study is the first to identify proteomic and metabolomic variations early (1 h and 1 day) postmortem that are linked to differences in early (6 h) postmortem pH values and to tenderness differences at 1 day postmortem. This study integrates postmortem biochemical features (protein degradation, proteome, and metabolome variations) to postmortem pH decline and eating quality of beef steaks. Potential biomarkers of more rapid postmortem metabolism linked to earlier tenderization in beef are suggested. Identification of these biochemical features will assist in predicting the eating quality of beef products.

Distinct myofibrillar sub-proteomic profiles are associated with the instrumental texture of aged pork loin.

Fresh pork tenderness contributes to consumer satisfaction with the eating experience. Postmortem proteolysis of proteins within and between myofibrils has been closely linked with pork tenderness development. A clear understanding of the molecular features associated with pork tenderness development will provide additional targets and open the door to new solutions to improve and make pork tenderness development more consistent. Therefore, the objective was to utilize liquid chromatography and mass spectrometry with tandem mass tag (TMT) multiplexing to evaluate myofibrillar sub-proteome differences between pork chops of different instrumental star probe values. Pork loins (N = 120) were collected from a commercial harvest facility at 24 h postmortem. Quality and sensory attributes were evaluated at 24 h postmortem and after ~2 weeks of postmortem aging. Pork chops were grouped into 4 groups based on instrumental star probe value (group A,x¯â€…= 4.23 kg, 3.43 to 4.55 kg; group B,x¯â€…= 4.79 kg, 4.66 to 5.00 kg; group C,x¯â€…= 5.43 kg, 5.20 to 5.64 kg; group D,x¯â€…= 6.21 kg, 5.70 to 7.41 kg; n = 25 per group). Myofibrillar proteins from the samples aged ~2 wk were fractionated, washed, and solubilized in 8.3 M urea, 2 M thiourea, and 1% dithiothreitol. Proteins were digested with trypsin, labeled with 11-plex isobaric TMT reagents, and identified and quantified using a Q-Exactive Mass Spectrometer. Between groups A and D, 54 protein groups were differentially abundant (adjusted P < 0.05). Group A had a greater abundance of proteins related to the thick and thin filament and a lesser abundance of Z-line-associated proteins and metabolic enzymes than group D chops. These data highlight that distinct myofibrillar sub-proteomes are associated with pork chops of different tenderness values. Future research should evaluate changes immediately and earlier postmortem to further elucidate myofibrillar sub-proteome differences over the postmortem aging period.

A primary goal of meat production is to efficiently produce safe, high-quality products. Competing interests within the goal complicate this seemingly simple aspiration. Consequently, it is necessary to emphasize efforts to enhance our comprehension of biological and molecular factors that influence quality, safety, and efficient meat production. This experiment aimed to define the proteomic profiles of the myofibrillar fraction of fresh pork with differing quality traits. Myofibrils from aged pork chops with a range of tenderness levels were used to achieve this objective. Fifty-four proteins were differentially abundant between the divergent tenderness groups. This was due to the expression profile of proteins in muscle and/or changes in proteins in the myofibrillar fraction during postmortem aging. These results inform and direct the development of antemortem and postmortem applications to ensure success in producing high-quality pork.

Association of calpain and calpastatin activity to postmortem myofibrillar protein degradation and sarcoplasmic proteome changes in bovine Longissiumus lumborum and Triceps brachii.

The aim of this study was to determine the extent to which calpastatin (CASN) variants (based on two chromatographic peaks; CASN-P1 and CASN-P2) explain variation in µ-calpain autolysis, protein degradation, and changes in the sarcoplasmic proteome observed during postmortem aging of beef. The Longissimus lumborum (LL) and Triceps brachii (TB) muscles were obtained from six crossbred steers and samples prepared from day 0, 1 and 7 postmortem (pm). The decline of CASN activity during aging was due to decrease of CASN-P2 in both muscles. The CASN-P2:µ-calpain ratio at day 0 was greater for TB, which presented lesser calpain autolysis, myofibrillar protein degradation, and fewer sarcoplasmic proteome changes during aging. Changes in abundance of Heat shock protein 70 family in the sarcoplasmic fraction were positively associated to proteolysis during aging, with greater differences in LL.

Cytokine effects on maturation of the phagosomes containing Mycobacteria avium subspecies paratuberculosis in J774 cells.

Mycobacterium avium subspecies paratuberculosis (M. a. ptb) is an intracellular pathogen of macrophages. Intracellular survival of several species of pathogenic mycobacteria is dependent on inhibition of maturation of the phagosomes containing these pathogens into functional phagolysosomes. In activated macrophages, however, this capacity is reduced, leading to increased bacterial killing. It is the hypothesis of this study that there is increased acidification and maturation of the phagosome containing M. a. ptb in interferon gamma and lipopolysaccharide (IFN-gamma/LPS) activated macrophages. In activated macrophages colocalization of M. a. ptb with either a marker of acidic compartments (Lysotracker Red) or compartments containing a late phagosome maturation marker lysosome-associated membrane protein-1 (Lamp-1) were evaluated by laser confocal microscopy. Intracellular survival of M. a. ptb in activated macrophages was evaluated directly using differential fluorescent live/dead staining. The results of this study demonstrated increased colocalization of both Lysotracker Red and Lamp-1 with FITC labeled M. a. ptb, which correlated with decreased survival of M. a. ptb within activated macrophages.