Antigenic relationship of legume seed proteins to the 7S seed storage protein of soybean

The Vicilin protein (Vigna radiata L.) of mung bean as a functional food

Purpose

The hypocholesterolemic activity of legume vicilins and the structural homology among mung bean, soybean and adzuki bean vicilins (8S) suggest that this protein may play a role in lipid metabolism. Thus, in the present study, the authors aim to isolate the mung bean vicilin and assess its in vitro effect on 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG CoAr), the enzyme responsible for endogenous cholesterol synthesis.

Design/methodology/approach

Chromatographic and electrophoretic characterization identified the molecular mass and polypeptide composition of mung bean vicilin. The hydrolysate of this globulin was obtained by sequential hydrolysis with pepsin-pancreatin and the fragments were characterized by molecular filtration, SDS PAGE and HPLC.

Findings

The molecular mass of vicilin was estimated as 158.23 at ± 10 kDa and SDS-PAGE revealed that the 8S globulin protein comprises four bands corresponding to polypeptides of 61, 48, 29 and 26 kDa. Fractions 10, 12, 14, 22 and 32 of the eluate from Sephadex G-25 exhibited significant inhibition of HMG CoAr.

Originality/value

The correspondence of the chromatographic profile of the peptide fractions with hypocholesterolemic activity suggests that the composition and chemical structure of these peptides are essential to their physiological effectiveness. The beneficial effects of mung bean vicilin identified in this study will support the characterization of this protein as a functional compound.

Advances in the molecular biology of plant seed storage proteins

Plant seed storage proteins were among the first proteins to be isolated (20); however, only recently, as a result of using molecular biology techniques, have the amino acid sequences of many of these proteins been determined. With the accumulation of amino acid sequence data for many vicilin-type storage proteins much has been learned concerning the location of conserved amino acid regions and other regions which can tolerate amino acid sequence variation. Combining this knowledge with recent advances in plant gene transfer technologies will allow molecular biologists to correct (by using amino acid replacement mutations) the sulfur amino acid deficiency inherent to bean seed storage proteins. The development of more nutritious soybean and common bean seeds will be of benefit to programs involving human and animal nutrition.