This study investigated the feasibility of oxidative modification with glucose oxidase (GluOx) to enhance the rheological and gelling properties of myofibrillar protein. Differential oxidative modifications of myofibrillar protein (MP) by hydroxyl radicals generated in an enzymatic system with glucose oxidase (GluOx) in the presence of glucose/FeSO4 compared to a Fenton system (H2O2/FeSO4) were investigated. Firmer and more elastic MP gels were produced by the GluOx-oxidizing system than by the Fenton system at comparable H2O2 levels due to an altered radical reaction pathway. The study further explored the effect of GluOx-mediated oxidation on the efficacy of transglutaminase (TGase) cross-linking of MP in 0.6 M NaCl and the rheological properties of GluOx oxidation/TGase treated MP in MP–lipid emulsion composite gels. The GluOx-mediated oxidation promoted the formation of both soluble and insoluble protein aggregates via disulfide bonds and occlusions of hydrophobic groups. The subsequent TGase treatment converted protein aggregates into highly cross-linked polymers. MP–lipid emulsion composite gels formed with such polymers exhibited markedly enhanced gelling capacity: up to a 4.4-fold increase in gel firmness and a 3.5-fold increase in gel elasticity over untreated protein. Microstructural examination showed small oil droplets dispersed in a densely packed gel matrix when MP was oxidatively modified, and the TGase treatment further contributed to such packing. Comparison of the modification of MP via GluOx oxidation/TGase cross-linking pathway under different salt concentrations (0.3 and 0.6 M NaCl) showed different patterns of MP cross-linking, resulting in different extents of aggregation. Under low-salt condition (0.3 M NaCl), the GluOx/TGase treatment increased the gel strength to the same level as those treated with TGase in 0.6 M NaCl, suggesting a potential application of GluOx/TGase for improving gel strength in low ionic strength conditions. Finally, the application of GluOx oxidation in the development of emulsion-type sausages was studied. The GluOx oxidation/TGase cross-linking improved the textural properties (firmness, chewiness, and rupture force) of emulsion-type sausages under both salt levels (P < 0.05). Under low-salt condition (1.5% NaCl), GluOx/TGase treatment can increase the sausage binding strength to the same level as the control sample under high-salt condition (3% NaCl). The GluOx oxidation/TGase treatment shows promise to improve the textural properties of emulsified meat products. However, the significant decrease of a* value and increase of b* value indicated GluOx-induced color deterioration.

L’endostatine est le fragment C-terminal du collagène XVIII libéré dans la matrice extracellulaire par clivage enzymatique. C'est un inhibiteur endogène de l’angiogenèse et de la croissance tumorale. L'endostatine inhibe la prolifération et la migration des cellules endothéliales induite par le Fibroblast Growth Factor-2 ou le Vascular Endothelial Growth Factor et elle inhibe la croissance de 65 types de cellules tumorales. L’endostatine fait actuellement l’objet d’essais cliniques pour le traitement de différents cancers son mécanisme d’action est encore mal connu. Nous avons caractérisé par résonance plasmonique de surface (SPR) les interactions établies par l'endostatine avec les intégrines αvβ3 et α5β1 qui sont surexprimées à la surface des cellules endothéliales activée. Nous avons identifié le site de fixation l'endostatine sur les intégrines, proposé un modèle de structure du complexe formé par l'endostatine et l'intégrine αvβ3 et montré que l'endostatine ne peut pas se lier simultanément aux intégrines et aux chaînes d'héparane sulfate présentes à la surface cellulaire. Pour identifier des partenaires supplémentaires de l'endostatine, nous avons développé des puces à protéines et à glycosaminoglycanes basées sur la SPR et capables de suivre jusqu'à 400 interactions simultanément. Nous avons identifié neuf partenaires de l'endostatine (le dermatane sulfate, la transglutaminase-2, les collagènes I, IV et VI, le peptide amyloïde β1-42, et des protéines matricellulaires dont SPARC et thrombospondine-1). Nous avons montré que l’endostatine se fixe avec une forte affinité (KD ~ 6 nM) sur la transglutaminase-2 et que cette interaction nécessite la présence de calcium mais que l'endostatine n'est pas un substrat donneur d'acyle de l'enzyme. Nous avons montré que le réseau d'interactions de l'endostatine est enrichi en protéines contenant des modules EGF (Epidermal Growth Factor). Cela offre de nouvelles perspectives pour l'identification d'autres partenaires et donc de nouvelles fonctions de l'endostatine. Des protéines contenant des modules EGF comme la fibrilline-1, composant des fibres élastiques, et des protéines de l'immunité innée par exemple sont des partenaires potentiels de l'endostatine / Endostatin is the carboxyl-terminal fragment of collagen XVIII released in the extracellular matrix by proteolytic cleavage. It inhibits angiogenesis and tumor growth. Endostatin inhibits the proliferation and migration of endothelial cells induced by Fibroblast Growth Factor-2 and Vascular Endothelial Growth Factor and it inhibits 65 different tumor types. Endostatin is currently under clinical trials for several tumors. We have used surface plasmon resonance (SPR) binding assays to characterize interactions between endostatin and α5β1 or αvβ3 integrins which are over-expressed at cell surface of actived endothelial cell. We have identified the binding site of endostatin on those integrins, and we have built a molecular modeling of the endostatin/integrin αvβ3 complex. We have shown that endostatin can not bind simultaneously to integrins and to heparan sulfate. In order to identify new partners of endostatin we have developed glycosaminoglycan and protein arrays based on SPR detection. We have found nine new partners of endostatin include glycosaminoglycans (chondroitin and dermatan sulfate), matricellular proteins (thrombospondin-1 and SPARC), collagens (I, IV and VI), the amyloid peptide Aβ(1-42), and transglutaminase-2 (TG-2). We have shown that endostatin binds to transglutaminase-2 with an high affinity (KD ~ 6 nM) in a calcium-dependent manner. Enzymatic assays indicated that, in contrast to other extracellular matrix proteins, endostatin is not a glutaminyl substrate of TG-2, but would rather be an acyl acceptor. The endostatin network comprises a number of extracellular proteins containing EGF domains (Epidermal Growth Factor), and able to bind calcium. Depending on the trigger event, and on the availability of its members in a given tissue at a given time, the endostatin network might be involved either in the control of angiogenesis, and tumor growth, or in neurogenesis and neurodegenerative diseases