No abstract

The present report overviews a new family of bovine serpins able to inhibit pseudo-irreversibly initiator and effector caspases, a group of cysteine proteases in charge of cell dismantling during apoptosis, a finely regulated cell death process. The 8 members identified at the gene level showed a high homology with human SERPINA3 and were therefore designed bovSERPINA3-1 to A3-8. At least six of them are able to inhibit caspases. Two of them (bovSERPINA3-1 and A3-3) have been purified from bovine muscle and extensively investigated during these last years. After a general presentation of the serpin superfamily, the kinetic aspects of their interaction with human caspases 3 and 8 were studied and findings obtained suggest that caspases could be their target enzymes in living cells. In muscle and primary myoblast in culture, they showed an intracellular localization and because of their high level in blood, they can be exported. Two biological functions (potential regulator of apoptosis and expression during myoblast differentiation) were investigated and it was concluded that they are very likely an efficient regulator of apoptosis, a proposal supported by their high expression in proliferating myoblast (cell survival is essential during this differentiation phase) but not in myotubes.

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.

Since years, serine proteases and their inhibitors were an enigma to meat scientists. They were indeed considered to be extracellular and to play no role in postmortem muscle proteolysis. In the 1990's, we observed that protease inhibitors levels in muscles are a better predictor of meat tenderness than their target enzymes. From a practical point of view, we therefore choose to look for serine protease inhibitors rather than their target enzymes, i.e. serine proteases and the purpose of this report was to overview the findings obtained. Fractionation of a muscle crude extract by gel filtration revealed three major trypsin inhibitory fractions designed as F1 (Mr:50-70 kDa), F2 (Mr:40-60 kDa) and F3 (Mr:10-15kD) which were analyzed separately. Besides antithrombin III, an heparin dependent thrombin inhibitor, F1 and F2 comprised a large set of closely related trypsin inhibitors encoded by at least 8 genes bovSERPINA3-1 to A3-8 and able to inhibit also strongly initiator and effector caspases. They all belong to the serpin superfamily, known to form covalent complexes with their target enzymes, were located within muscle cells and found in all tissues and fluids examined irrespective of the animal species. Potential biological functions in living and postmortem muscle were proposed for all of them. In contrast to F1 and F2 which have been more extensively investigated only preliminary findings were provided for F3. Taken together, these results tend to ascertain the onset of apoptosis in postmortem muscle. However, the exact mechanisms driving the cell towards apoptosis and how apoptosis, an energy dependent process, can be completed postmortem remain still unclear.

The aim of the present work is to set up a production process of goat milk-based yoghurt. Six (06) kinds of yoghurt have been prepared: a mixed unflavored yoghurt with 50% cow & goat milk, a mixed flavored yoghurt with 50% cow & goat milk, an unflavored 100% goat-milk-based yoghurt, a flavored 100% goat-milk-based yoghurt, two types of 100% goat milk-based yoghurts supplemented with natural honey. Results of bacteriological analyses of finished products showed the total absence of pathogenic bacteria Staphylococcus aureus and salmonella as well as the indicator hygiene bacteria like the fecal and total coliforms. Sensory analyses revealed that 100% goat-milk-based yoghurts are always better appreciated in the other categories (flavored or unflavored) compared to 50% mixed yoghurts. Sensory analyses reported that yoghurts made with honey (HGM1 and HGM2) were richer in carbohydrates (10.5g) and in energy (89.1 kilocalories) against natural yoghurts and flavored yoghurts, which recorded a carbohydrate content of 5.3g and 68.3 kilocalories. The protein contents were assessed at 3.9g. Levels of lipids were at 3.5g together with amounts in minerals such like: calcium, phosphorous, potassium and sodium which reached respectively 168 mg, 114 mg, 203 mg and 58 mg.