BIOCHEMICAL STUDIES ON BLACK GRAM (Phaseolus mungo L.) SEEDS: AMINO ACID COMPOSITION AND SUBUNIT CONSTITUTION OF FRACTIONS OF THE PROTEINS

ABSTRACT The protein fractions, albumins, globulins, prolamins and glutelins, of black gram ( Phaseolus mungo L.) seeds were characterized for their amino acid compositions, isoelectric points, and subunit constitutions Globulins which formed 81% of the solubilized proteins were devoid of sulfur containing amino acids. Sulfur containing amino acids and threonine were deficient in total proteins of the seeds with 27.6 and 78.8 as their respective amino acid scores. Chemical scores of albumin, globulin, prolamin, and glutelin fractions were 64, 0, 56 and 70.7 respectively. The predicted biological values in human nutrition varied from 0 for globulins to 110 for glutelins and it was 14.9 for total proteins in the seeds. Dissolution of globulins was minimum in a pH range, 5.3‐5.9. Isoelectric focusing in a dissociating medium indicated that the majority of globulin subunits were acidic. Globulins, however, had two basic subunits with isoelectric points at 8.42 and 8.65. Two dimensional slab gel electrophoresis, with a phenol‐acetic acid‐mercaptoethanol‐urea (PAMU) system in the first dimension and sodium dodecyl sulfate (SDS) system in the second dimension suggested that the mobilities of proteins in PAMU and SDS systems were based on the related parameters.