Physicochemical and Structural Properties of 8S and/or 11S Globulins from Mungbean [Vigna radiata(L.) Wilczek] with Various Polypeptide Constituents

Abstract

Two kinds of globulins, 8S and 11S globulins, with various polypeptide constituents, were well fractionated from acid- and salt-extracted mungbean globulins using DEAE-Sepharose fast flow column chromatography. The physicochemical and conformational properties, including amino acid composition, surface charge and hydrophobicity, free sulfhydryl group (SH) and disulfide bond (SS) contents, protein solubility, thermal and emulsifying properties, as well as secondary and tertiary conformations, were evaluated. Remarkable differences in polypeptide composition, surface charge and hydrophobicity, SS contents, protein solubility, thermal and emulsifying properties, and secondary and tertiary conformations were observed between 8S and 11S globulins. The physicochemical and conformational properties of the vicilins also varied with the heterogeneity of their polypeptides, but to a relatively limited extent. The emulsifying ability of these globulins was distinctly dependent on their protein solubility (or net charge), surface hydrophobicity and polypeptide heterogeneity. The thermal properties were similar among various vicilins, but distinctly different between the vicilins and 11S globulins. The circular dichrosim spectral analyses revealed that there were no marked differences in secondary and tertiary conformations between various vicilins, but the secondary, tertiary and quaternary conformations of 11S globulins were much more unordered and flexible than the vicilins. These results suggested good relationships between the physicochemical properties and conformational features of these globulins from mungbean, which could be useful for the utilization of these proteins in the food industry, and providing a working direction of mungbean breeding or protein engineering to improve its physicochemical properties.