Fractionation and biochemical characterization of moth bean (Vigna aconitifolia L.) proteins

Moth bean seeds contained 24 g/100 g protein (micro-Kjeldahl N×6.25) on a dry weight basis. Among the solvents tested, 0.1 mol/l NaOH and 0.1 mol/l sodium phosphate buffer (pH 7.5) were the most effective in solubilizing the seed flour proteins. Native isoelectric focusing of the total soluble proteins indicated moth seed proteins to be acidic (pI range 4.55–<6.55) with a few neutral to alkali proteins (pI range 7.35–9.3). Globulin fraction dominated the seed protein composition accounting for ∼64 g/100 g of the total soluble proteins in the seeds. The globulin fraction was composed of at least three major glycopeptides with an estimated molecular mass range of 45–55 kDa and several additional polypeptides in the 14–32 kDa range. Sulfur amino acids were the first limiting amino acids in the seed flour proteins. Native and heat denatured albumin and glutelin fractions were readily hydrolysed, in 30 min, by pepsin at 37 °C. Although resistant to proteolysis in the native state, heat denatured globulin (100 °C, 30 min, boiling water-bath) was completely digested to <14 kDa polypeptides by pepsin in 30 min at 37 °C. Moth bean was devoid of detectable phytohemagglutinating activity and had low trypsin inhibitory activity when compared with the corresponding activities in soybeans.