Early postmortem degradation of actin muscle protein in Algerian Sahraoui dromedaries

The present study aimed to evaluate actin degradation during the early postmortem time in Longissimus Lumborum muscle according to Sahraoui dromedary's age. A sample of eight males, young (2 years old) and adult (8 years old) dromedaries, was used to investigate meat quality traits and actin proteolysis during the conversion of muscle to meat. Results demonstrated higher pH values in young compared to adult with a polyphasic pH drop profile. While, age did not affect drip loss (DL) and the values at 72 h postmortem varied from 5 to 9%. Western blot revealed that actin proteolysis occurred since 1 h postmortem and that it was affected by age and postmortem time. In particular, the 32 and 25 kDa actin fragments could be potential markers of ongoing meat tenderization.

Assessment of Stress by Serum Biomarkers in Calves and Their Relationship to Ultimate pH as an Indicator of Meat Quality

Simple Summary

The routine handling of cattle during the rearing period and during antemortem events is an inevitable source of animal stress that can have negative impacts on the quality of meat, resulting in economic losses for the meat industry. This study assesses the breed, the farm management system, and the pre-mortem handling of animals and their impact on serum stress biomarkers, as well as their relationship with pH_u. The findings indicate that breed, together with farm management, had the highest impact; cortisol, lactate, and serum amyloid A were identified as potential stress biomarkers in relation to pH_u. We believe that these findings might help in the assessment of stress in cattle at the stage prior to slaughter.

Abstract

Seventy-eight calves from Asturiana de los Valles, Retinta, and Rubia Gallega breeds, under extensive and intensive farm systems and animal mixing and non-mixing conditions, and during the transport and lairage in slaughterhouses, were studied. This research aimed to study the effect of breed, farm system and mixing conditions on serum biomarkers (cortisol, lactate, glucose, serum amyloid A, haptoglobin, and C-reactive protein) and their relationship with pH_u at slaughter time, and to evaluate the response of the serum biomarkers of calves throughout fattening period. Moreover, this study aims to evaluate the response of the biomarkers in each breed during the fattening period. At slaughter time, cortisol and lactate were affected by BreedxFarm; Retinta showed the opposite pattern to the others and revealed the highest glucose in extensive farm systems. Rubia Gallega in mixing revealed the highest Amyloid A and haptoglobin. Extensive calves in mixing conditions showed the highest glucose. There was a relationship among the variables cortisol, lactate, Amyloid A, and pH_u. Slaughter time was a major stressor, and the stress response was mainly affected by breed. At slaughter, several biomarkers should be considered.

Measuring quantitative proteomic distance between Spanish beef breeds

Estimates of quantitative proteomic distance between populations have not been reported to date. Here, quantitative proteomic distances between three Spanish bovine breeds (Asturiana de los Valles, AV; Retinta, RE; and Rubia Gallega, RG) were estimated from two-dimensional electrophoresis profiles of meat samples of longissimus thoracis muscle at 2 h post-mortem. Statistically significant distances were detected between AV/RG and the most genetically different RE breed, using the novel QD measure of quantitative proteomic distance. In total, 18 differentially abundant myofibrillar and sarcoplasmic proteins/isoforms contributing to proteomic distances between breeds were confidently identified by tandem mass spectrometry. The fast skeletal myosin regulatory light chain 2 followed by other five interacting proteins exhibited the most pronounced relative change between breeds. In addition, most differentially represented proteins could be associated with variations in meat tenderness. Therefore, they could be candidate biomarkers for molecular breeding programs and authentication of the three Spanish beef breeds.

Identification of Potent ACE Inhibitory Peptides from Wild Almond Proteins

In this study, the production, fractionation, purification and identification of ACE (angiotensin-I-converting enzyme) inhibitory peptides from wild almond (Amygdalus scoparia) proteins were investigated. Wild almond proteins were hydrolyzed using 5 different enzymes (pepsin, trypsin, chymotrypsin, alcalase and flavourzyme) and assayed for their ACE inhibitory activities. The degree of ACE inhibiting activity obtained after hydrolysis was found to be in the following order: alcalase > chymotrypsin > trypsin/pepsin > flavourzyme. The hydrolysates obtained from alcalase (IC₅₀ = 0.8 mg/mL) were fractionated by sequential ultrafiltration at 10 and 3 kDa cutoff values and the most active fraction (<3 kDa) was further separated using reversed phase high-performance liquid chromatography (RP-HPLC). Peptide sequence identifications were carried out on highly potential fractions obtained from RP-HPLC by means of liquid chromatography coupled to electrospray ionization and tandem mass spectrometry (LC-ESI-MS/MS). Sequencing of ACE inhibitory peptides present in the fraction 26 of RP-HPLC resulted in the identification of 3 peptide sequences (VVNE, VVTR, and VVGVD) not reported previously in the literature. Sequence identification of fractions 40 and 42 from RP-HPLC, which showed the highest ACE inhibitory activities (84.1% and 86.9%, respectively), resulted in the identification of more than 40 potential ACE inhibitory sequences. The results indicate that wild almond protein is a rich source of potential antihypertensive peptides and can be suggested for applications in functional foods and drinks with respect to hindrance and mitigation of hypertension after in vivo assessment.

PRACTICAL APPLICATION

This study has shown the potential of wild almond proteins as good sources for producing ACE-inhibitory active peptides. According to this finding, peptides with higher ACE inhibitory activities could be released during the gastrointestinal digestion and contribute to the health- promoting activities of this natural protein source.

Caspases and Thrombin Activity Regulation by Specific Serpin Inhibitors in Bovine Skeletal Muscle

In living cells, after activation, protein inhibitors constitute the last step of proteases activity regulation. This review intends to provide original information about a group of bovine muscle serine proteases inhibitors belonging to the Serpin superfamily and characterized at the gene and protein level. This report is the only one and the first to provide much information on this group of proteases inhibitors of the serpin type and their potential biological functions. Amongst the eight genes identified in bovine, three serpins were purified from the muscle tissue and characterized. These are two members of the bovSERPINA3 family, i.e., bovSERPINA3-1 and A3-3, and the last one is antithrombin III (AT-III or BovSERPINC1). BovSERPINA3 family comprises at least eight protein members encoded by different genes mapped on chromosome 7q23-q26 cluster. BovSERPINA3-1 and A3-3 were shown to locate within muscle cells and are cross-class inhibitors strongly active against trypsin as well as against human initiator and effector caspases 8 and 3. They constitute a key apoptosis control in mammals. They were thus expressed in proliferating and confluent myoblasts phases where cells must be alive but not in myotubes. Antithrombin III inhibits trypsin and, in a heparin dependent manner, thrombin. AT-III and its mRNA were expressed in muscle cells and in differentiating primary myoblasts in culture.

Lactobacillus sakei CRL1862 improves safety and protein hydrolysis in meat systems

AIMS

The capacity of Lactobacillus sakei CRL1862 to prevent the growth of pathogens and its ability to degrade sarcoplasmic and myofibrillar proteins in pork meat systems was evaluated. In addition, basic safety aspects of Lact. sakei CRL1862 such as production of biogenic amines and antibiotic susceptibility were addressed.

METHODS AND RESULTS

The bacteriocin-producing Lact. sakei CRL1862 showed respectively bactericide and bacteriostatic effect against Listeria monocytogenes and Staphylococcus aureus in beaker sausage assay during 9 days of storage at 22 °C. The hydrolytic effect of Lact. sakei CRL1862 on protein extracts was evaluated by SDS-PAGE and reverse phase HPLC. A more pronounced proteolysis was evidenced in inoculated sarcoplasmic proteins compared with myofibrillar extracts with the generation of predominantly hydrophilic peptides and increase of total free amino acids concentration. Lactobacillus sakei CRL1862 produced neither histamine nor tyrosine and exhibited no resistance to the antibiotics assayed.

CONCLUSIONS

Lactobacillus sakei CRL1862 effectively controlled the growth of L. monocytogenes and Staph. aureus; moreover, it was able to hydrolyse pork meat extracts generating peptides and amino acids, which may improve hygienic and sensorial attributes of fermented meat products.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of an integrated approach to evaluate the major traits of Lact. sakei CRL1862 showed it can be applied as an autochthonous functional starter in meat fermentation.

Characterization of peptides released by in vitro digestion of pork meat

The main objective of this work was to identify and characterize the peptides generated by simulated gastrointestinal digestion of pork meat (longissimus dorsi) by the sequential action of pepsin and pancreatin. The obtained hydrolysate was analyzed by liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer equipped with a nanoelectrospray ionization source (nano LC-ESI-MS/MS). Using this technique 51 different peptides were identified in the hydrolysate, corresponding to fragments of the main structural muscle proteins and some well-known sarcoplasmic proteins. To the best of our knowledge, this constitutes the highest number of peptides identified in pork meat digests. Peptide fragment size ranged from six to sixteen amino acids, being rich in proline residues and thus making them more resistant to further degradation by digestive enzymes. The present study constitutes a clear evidence of the extensive degradation that pork muscle proteins would undergo after gastrointestinal digestion, giving rise to a wide variety of short peptides. So, the use of in vitro digestion contributes to a better knowledge about the generation of peptides from diets with high protein quality.

Angiotensin I-converting enzyme inhibitory peptides generated from in vitro gastrointestinal digestion of pork meat

The main purpose of this work was to study the generation of Angiotensin I-converting enzyme inhibitory (ACEI) peptides after gastrointestinal digestion of pork meat by the action of pepsin and pancreatin at simulated gut conditions. The hydrolysate was further subjected to reverse phase chromatography in order to separate the fractions with ACEI activity. Using MALDI-TOF/TOF mass spectrometry, 12 peptides were identified in these fractions. It is worth highlighting the novel peptides ER, KLP, and RPR with IC(50) values of 667 microM, 500 microM, and 382 microM, respectively. Results obtained by MALDI-TOF/TOF mass spectrometry were complemented by a second approach consisting of the analysis of the hydrolysate directly by nanoLC-ESI-MS/MS followed by a study of the obtained sequences and comparison with known ACEI peptide sequences. By using these two approaches, a total of 22 peptides were selected for its synthesis and further in vitro assay of ACEI activity. The strongest ACE inhibition was observed for peptide KAPVA (IC(50) = 46.56 microM) followed by the sequence PTPVP (IC(50) = 256.41 microM). Sequence similarity searches revealed that these two peptides derive from muscle titin, constituting the first identified ACEI peptides coming from this protein. This is also the first time that ACEI sequences MYPGIA and VIPEL have been reported. Other identified and synthesized sequences showed less ACEI activity. The obtained results evidence the potential of pork meat proteins as a source of antihypertensive peptides after gastrointestinal digestion.

Oligopeptides arising from the degradation of creatine kinase in Spanish dry-cured ham

During the processing of dry-cured ham many biochemical changes occur, including the degradation of muscle proteins. These changes are due to the intense action of endogenous proteolytic enzymes. In the present study, the isolation and identification of a large number of peptides derived from creatine kinase has been achieved for the first time in dry-cured ham. A total of 58 peptides coming from different regions of the protein have been identified by mass spectrometry. This study provides evidence for the extensive degradation of creatine kinase during the processing of dry-cured ham as well as the role played by endo- and exopeptidases in the generation of small peptides and free amino acids from polypeptides. These peptides are important in the development of characteristic sensory properties associated with dry-cured ham.

Naturally generated small peptides derived from myofibrillar proteins in Serrano dry-cured ham

A proteomic approach has been carried out to investigate the extensive proteolysis occurring in the processing of Serrano ham. In this study, a total of 14 peptide fragments derived from myosin light chain I and titin have been identified for the first time. Nine of these peptides originated from myosin light chain I protein, with the loss of dipeptides at the N-terminal position observed in some of them. This suggests that dipeptidyl peptidases are involved in the generation of dipeptides, which contribute to the generation of the characteristic taste associated with Serrano ham. The other five peptides came from the PEVK region of the titin protein. This region is believed to confer elasticity to the sarcomere as well as the ability to bind calpains. The hypothetical action of mu-calpain and calpain 3 enzymes over this region would make these enzymes potentially responsible for protein breakdown during the early dry-curing stage.

Effect of cooking conditions on creatinine formation in cooked ham

The aim of this study was to evaluate the effect of different cooking procedures on the concentrations of creatine and creatinine and the ratio of creatinine/creatine in cooked ham. Two cooking methods (constant temperature and increasing temperature, constant T and DeltaT, respectively) were tested on different locations in porcine longissimus dorsi muscle and ham (semimembranosus, biceps femoris, and gluteus muscles). The results showed larger creatine conversion into creatinine in the surface layer than in the core as well as higher creatinine/creatine ratio values when applying the DeltaT in comparison to the constant T method. A correlation between the creatinine/creatine ratio and the heat treatment was established, and 15 samples of commercial cooked hams were analyzed to support these results. This creatinine/creatine ratio analyzed in the surface of the ham could be used as a rapid and nondestructive indicator to determine the effectiveness of the heat treatment in cooked ham processes.

Hydrophilic chromatographic determination of carnosine, anserine, balenine, creatine, and creatinine

A new HPLC procedure based on hydrophilic interaction chromatography (HILIC) has been developed for the simultaneous determination of carnosine, anserine, balenine, creatine, and creatinine in meat. This is the first time that HILIC has been directly applied to the study of meat components, having the advantage of not requiring complex cleanup and/or sample derivatization procedures. The chromatographic separation has been developed using a silica column (4.6 x 150 mm, 3 microm), and the proposed methodology is simple, reliable, and fast (<13 min per sample). The method has been validated in terms of linearity, repeatability, reproducibility, and recovery and represents an interesting alternative to methods currently in use for determining the mentioned compounds and other polar substances. The detection limits are 5.64, 8.23, 3.66, 3.99, and 0.06 microg/mL for carnosine, anserine, balenine, creatine, and creatinine, respectively.

Proteomic identification of actin-derived oligopeptides in dry-cured ham

An intense proteolysis of muscle proteins, mainly due to the action of endogenous proteolytic enzymes, has been reported to occur during the processing of dry-cured ham. This gives rise to an important generation of free amino acids and peptides of small size that contribute directly or indirectly to flavor characteristics of the final product. The nature and properties of the free amino acids generated during postmortem proteolysis have been well established. However, little is known about the identity of peptides generated during the processing of dry-cured ham. In the present paper, we describe the isolation (by ethanol precipitation followed by size exclusion and reverse phase chromatographies) and identification (by matrix-assisted laser desorption/ionization time-of-flight MS and collision-induced dissociation MS/MS) in a Spanish dry-cured ham of the following four oligopeptides: (A) TKQEYDEAGPSIVHR, (B) ITKQEYDEAGPSIVHRK, (C) DSGDGVTHNVPIYE, and (D) DSGDGVTHNVPIYEG. This is the first time that these peptide fragments have been reported in dry-cured ham at the end of processing. Sequence homology analysis revealed that the four peptides originated from muscle actin, indicating an extensive hydrolysis of this protein during dry-curing. Some of the cleavage sites corresponding to these fragments in actin were reproduced by other authors through the incubation of this myofibrillar protein in the presence of cathepsin D (EC 3.4.23.5), thus supporting a relevant action of this enzyme during the processing of dry-cured ham.

A fluorescence-based protocol for quantifying angiotensin-converting enzyme activity

The determination of angiotensin-converting enzyme (ACE) activity represents a useful tool in the study of different health pathologies, such as hypertension. This protocol describes a fluorescent assay for measuring ACE activity in vitro with high precision and sensitivity. The method relies on the ability of ACE to hydrolyse the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitro-L-phenylalanyl-L-proline. The generation of the fluorescent product o-aminobenzoylglycine can be continuously monitored, preferably using a microtiter-plate fluorometer, though the use of a conventional cuvette fluorometer would also be possible. The method has important advantages with respect to other assays, because it involves only a one-step reagent, is easy to carry out and allows the analysis of an elevated number of samples in shorter times. It can be completed in one and a half hours. In addition, the fact that all reagents are commercially available allows the rapid introduction of the assay into the laboratory.

Bovine muscle 20S proteasome: I. Simple purification procedure and enzymatic characterization in relation with postmortem conditions

Over the last decade, several sets of evidence support a possible contribution of the 20S proteasome to the meat tenderizing process. This assumption was emphasized by recent investigations demonstrating that the 20S proteasome was active in the absence of activators and exhibited endo- and exoproteolytic activities, a status often strongly debated before. In the present work, we developed a new rapid and simple purification procedure for muscle 20S proteasome and revisited the physicochemical properties of this complex in relation with the postmortem muscle environmental conditions, i.e. temperature, pH, osmolarity, etc. From a crude extract obtained from freshly excised muscle tissue, reasonable amounts of highly pure proteasome were prepared within a maximum of 4 days using only three chromatography steps. This purified proteasome was used to investigate the effect of pH, temperature, ionic strength and sodium dodecyl sulphate (SDS) on the major hydrolytic activities of this complex, i.e. trypsin-like (TL), chymotrypsin-like (CL) and peptidylglutamyl peptide hydrolase (PGPH) activities. Taken together, the data obtained suggest that the 20S proteasome constitutes a high hydrolytic potential in postmortem muscle conditions. To attest this finding, the 20S proteasome was further quantified by ELISA in at death and postmortem muscles including Longissimus, Rectus abdominis, Diaphragma pedialis and Tensor fascia latae bovine muscles. The primary conclusion was that time course changes in proteasome concentrations were not dependent on the kinetics of the pH fall. Secondly, the proteasome concentration in conditioned meat was in good agreement with previously reported proteolytic activity. Furthermore, the decrease in the muscle proteasome concentration can be considered as slow and this is particularly true in type 1 muscles for which the decrease in the amount of this complex did not exceed 7% during the first three days postmortem. This would suggest that the 20S proteasome was relatively stable during meat conditioning, a feature supporting a potential role in the meat tenderizing process.

Purification of bovine cathepsin B: proteomic characterization of the different forms and production of specific antibodies

Cathepsin B (EC 3.4.22.1) has been highly purified (14,225 fold) from bovine kidney by a rapid procedure that included the preparation of an enriched lysosomal extract, a selective fractionation with ammonium sulphate, size-exclusion chromatography, two cation-exchange chromatographies, and anion-exchange chromatography on diethylaminoethyl-Sephacel. After the last purification step, two hydrolytic peaks against Z-Phe-Arg-AMC were separated from each other, a minor peak corresponding to the cathepsin B single-chain form and a major one representing the double-chain form of cathepsin B. The single-chain form showed a molecular mass of 31 kDa on sodium dodecyl sulphate - polyacrylamide gel electrphoresis (PAGE) under reducing conditions, whereas the heavy chain of the double-chain form appeared as a doublet with molecular masses of 23.4 and 25 kDa, respectively. The identity of the different cathepsin B isoforms and the quality of the final enzyme preparation were confirmed by using two types of antibodies, one against a synthetic peptide sequence and one against purified cathepsin B. The proteomic study confirmed the identity of the different SDS-PAGE protein bands as cathepsin B isoforms and allowed the comparison and study of some structural differences between them at the level of their primary structures.

Purification and biochemical properties of dipeptidyl peptidase I from porcine skeletal muscle

Dipeptidyl peptidase I (DPP I; EC 3.4.14.1) was purified from porcine skeletal muscle after several steps such as heat treatment, ammonium sulfate fractionation, gel filtration chromatography, and HPLC anion exchange chromatography. The purified enzyme showed a native molecular mass of approximately 200 kDa on Sephacryl S-200 column chromatography. Two protein bands of 65 and 42 kDa were obtained by SDS-PAGE, indicating its oligomeric nature. Maximum activity was reached at pH 5.5 and 55 degrees C. DPP I shared some common substrate specificities, both on synthetic derivatives and on real peptides, with porcine muscle DPP III. The enzyme required reducing agents for full activation, although the halide requirement was not proved. DPP I was inhibited by the assayed cysteine peptidase inhibitors except p-CMB. The serine peptidase inhibitor 3, 4-DCI also inhibited the enzyme as did the divalent cations Co(2+), Mn(2+), and Zn(2+). On the basis of its properties, DPP I may contribute to the generation of dipeptides during the processing of meat and/or meat products, including cooked ham.