ROLE OF PEROXIDASE AND H2O2 IN CROSS-LINKING OF GLUTEN PROTEINS

Abstract

ABSTRACT The extent of protein cross-linking in wheat dough influences the viscoelastic properties of dough. We have studied peroxidase-mediated cross-linking of proteins in in vitro system using isolated wheat glutenin protein subunits. Isolated glutenin subunits were treated with peroxidase/H2O2 system as well as with H2O2 alone. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis of treated subunits under reducing and nonreducing conditions revealed that peroxidase/H2O2 was able to cross-link glutenin protein subunits by disulfide bonds and nondisulfide covalent cross-links. The fluorescence spectrum of cross-linked proteins indicated the presence of dityrosine. On the other hand, treatment of glutenin protein subunits with H2O2 alone formed disulfide cross-links only. Peroxidase purified from wheat bran showed thiol oxidase activity. By virtue of thiol oxidizing and peroxidatic activity, wheat bran peroxidase may be able to form disulfide and dityrosine cross-links in glutenin subunits. Based on the results, we have proposed a mechanism for the role of peroxidase and H2O2 in cross-linking gluten proteins. PRACTICAL APPLICATIONS Wheat milling industry generates a large amount of bran and it is a waste by-product. Peroxidase isolated from wheat bran cross-linked the glutenin protein subunits. Therefore, wheat bran peroxidase can be used as a dough improver to achieve required dough properties. The knowledge of role of peroxidase in dough formation could be used in wheat breeding programs to develop new wheat varieties. Gluten is a potential source for the manufacture of biodegradable films, and peroxidase could be a tool to control cross-linking gluten properties to obtain desired biofilm characteristics.