Glutenin is a protein that is generally found in wheat. It is mostly present in the endosperm (which makes wheat flour). The protein glutenin is constitute about 50% of the protein in wheat flour. Glutenin protein consists of low molecular weight and high molecular weight subunits that are bound together by disulfide bonds.
Together with gliadin proteins, glutenin forms a complex protein called the Gluten protein. Gluten protein provides elasticity to the dough and helps to rise during the bread-making process. It also provides shape and chewy texture to the bread.