Purification and characterization of caclium-binding soybean protein hydrolysates by Ca2+/Fe3+ immobilized metal affinity chromatography (IMAC)

Soybean protein hydrolysates (SPHs) can bind calcium in order to form soluble peptide-calcium complexes. However, amino acid composition and structural characteristics of the calcium chelating SPHs are still unclear. This study separated SPHs with calcium and iron immobilized metal affinity chromatography (IMAC), and examined the effects of SPHs with different amino acid composition on calcium binding capacity. Three fractions (FFe-1, FFe-2 and FFe-3) isolated with IMAC-Fe3+ were shown possessing increased Glu, Gln, Lys and Pro content from FFe-1 to FFe-3, and improved amount of bound calcium. Furthermore, the fractions adsorbed on IMAC-Ca2+ (Fe3+) were separated and identified with reverse-phase (RP)-HPLC and MALDI-TOF MS/MS. The results showed that the sequence of peptides from FCa-2 and FFe-3 fractions was DEGEQPRPFPFP.