The Structure-physicochemical Function Relationships Of Vicilins From Phaseolus Legumes

Phaseolus legumes are considered second only to soybeans in the importance of high-quality plant protein resources, due to their good nutritional value and functionality. The vicilin, a kind of glycoproteins, is the major storage protein in these legume proteins. The structure on functional properties of proteins is closely linked. Therefore, the study of the structure-physicochemical function relationships, for using of phaseolus legumes protein, to protein modification, processing and nutrition metabolism has important significance. In this paper, in-depth study of three kinds of vicilin physicochemical and functional properties of proteins, the structure of the functional properties of the mechanism from kidney, red and mung beans, build the structure-physicochemical function relationships. Main results are as follows:Red bean 7S globulins (vicilins) with different polypeptide constituents or heterogeneity were fractionated and purified using acidic extraction (at 0.5 M NaCl) and anion-exchange column chromatography. The physicochemical and conformational properties, including net charge and/or surface hydrophobicity (H0), protein solubility, thermal and emulsifying properties, as well as tertiary and/or quaternary conformations, were evaluated. There were distinct differences in zeta potential, H0, DSC characteristics, emulsifying activities and tertiary and/or quaternary conformations among the vicilins with different polypeptide constituents. The protein solubility as a function of pH and thermal stability of these vicilins were closely related to their surface charge and/or hydrophobicity. The emulsifying ability and the emulsion stability were closely dependent on the protein solubility and H0, and even the flexibility in tertiary and/or quaternary conformations. Additionally, mung bean globulins were researched by the same methods, these results suggested good relationships between the physicochemical properties and conformational features of in the same Phaseolus legumes.The physicochemical and conformational properties included amino acid composition, surface charge and hydrophobicity, protein solubility, emulsifying ability index (EAI) and emulsion stability index (ESI), as well as secondary, tertiary and/or quaternary conformations of three vicilins from kidney, red and mung beans were characterized and compared. The results suggested good relationships between the physicochemical properties and conformational features of the different Phaseolus legumes again. At pH 7.0 or 9.0, there were close relationships between the EAI and the flexibility in quaternary conformation, and between the ESI and the flexibility in tertiary conformation. This is the first observation to elucidate the importance of tertiary and/or quaternary conformations for the emulsifying properties of legumes vicilins. Additionally, an underlying mechanism of the emulsification process for the vicilins (trimeric form) with excellent emulsifying properties was proposed.Glycosylated proteins were prepared from kidney bean vicilin by using Maillard reaction with the glucose. The degree of glycosylation was increaseded with the increase of reaction time and the molar ratio of protein to glucose; glycosylation can improve the solubility and heat stability, reduce the surface hydrophobicity (H0) during the drying-heat, increase the EAI; glycosidation little effect on the secondary but some effect on the tertiary and/or quaternary conformations conformations of kidney bean vicilin.The results of this paper provided an important theoretical basis for utilization of the Phaseolus legumes resources, while provided the main research directions for the development of resources for beans.