ISOLATION AND FUNCTIONALITY TESTING OF LOW-MOLECULAR-WEIGHT GLUTENIN SUBUNITS

Various protein fractionation techniques have been applied to the isol ation and purification of milligram quantities of low molecular weight glutenin subunits (LMW-GS). No single technique was applicable to the purification of the majority of the subunits. Partial purification of certain LMW-GS was obtained using ion-exchange chromatography and rev ersed-phase HPLC. Preparations containing alpha- and gamma-type subuni t sequences did not strengthen dough when incorporated into a base flo ur, whereas preparations containing a subunit with an N-terminal methi onine residue (METSHIPGL-) did. Using preparative isoelectric focusing over a narrow pH range, it was possible to purify (to approximate to 90% purity) a B subunit that also had the N-terminal sequence of METSH IPGL-. This polypeptide, when incorporated into a base flour, had a do ugh strengthening effect in mixing trials, but less so than an equival ent amount of a high molecular weight glutenin subunit.