Solubilization, fractionation, and electrophoretic characterization of Inca peanut (Plukenetia volubilis L.) proteins.

Effects of different solvents, ionic strength, and pH on Inca peanut seed protein solubility were assessed by quantitatively analyzing solubilized proteins using Lowry and Bradford methods. Soluble proteins were fractionated using Osborne procedure and the polypeptide composition of solubilized proteins was determined by one dimensional 25 % monomer acrylamide linear gradient SDS-PAGE. Osborne protein fractions were analyzed by the 2D gel electrophoresis. Total seed proteins were efficiently solubilized by 2 M NaCl among the tested solvents. The soluble seed proteins registered a minimum solubility at pH ~4.0. Osborne protein fractions, albumins, globulins, prolamins, and glutelins accounted for 43.7, 27.3, 3.0, and 31.9 %, respectively, of the total aqueous soluble proteins. Soluble seed flour proteins are mainly composed of polypeptides in the MW range of 6-70 kDa of which the predominant polypeptides were in the 20-40 kDa range. Prolamin fraction was mainly composed of four polypeptides (MW < 15 kDa). Glycoprotein staining indicated 32-35 and <14 kDa peptides to be positive.