Modulation of the secondary and tertiary structures of African yam bean (Sphenostylis stenocarpa) seed globulins, albumins and protein concentrate by pH and NaCl
Comfort F. Ajibola, Tayo N. Fagbemi, Rotimi E. Aluko
Journal of Food Biochemistry Volume 41, Issue 2 e12321
African yam bean (Sphenostylis stenocarpa) seed flour was extracted with 0.5 M NaCl and the supernatant dialyzed against water to obtain two protein products, the water-soluble albumin and water-insoluble globulin. The flour was also extracted separately with alkaline water followed by acid-induced protein precipitation at pH 5.0 to produce a protein concentrate. Amino acid composition was similar for the three protein products and showed a low Arg/Lys ratio. The three protein products had higher contents of the α-helix fraction than the β-strand but the level of unordered secondary structure was highest at pH 8.0. The near-UV chromatograms showed phenylalanine and tyrosine transitions in the albumin, whereas only the phenylalanine transition was seen in globulin and protein concentrate. Addition of increasing levels of NaCl led to increased structural rigidity in the albumin and protein concentrate but not so much in the globulin.
African yam bean, albumin, amino acid composition, circular dichroism, globulin, pH, NaCl, protein concentrate, protein conformation