Role of Peroxidase and H2O2 in Cross-Linking of Gluten Proteins.

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 crosslink
glutenin protein subunits by disulfide bonds and nondisulfide covalent crosslinks.
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.