title: A study of the soluble complexes formed during calcium binding by soybean protein hydrolysates.
abstract: The soluble complexes formed between hydrolyzed soybean protein and calcium at pH 7.4 were investigated using dialysis, gel chromatography, and Fourier transform infrared spectrometry (FTIR). The results demonstrate that the amount of calcium bound was significantly different for soybean protein hydrolysates obtained using the proteases neutrase, flavourzyme, protease M, and pepsin. Maximum levels of calcium binding (66.9 mg/g) occurred with hydrolysates produced using protease M. Peptide fragments exhibiting high calcium binding capacity had molecular weights of either 14.4 kDa or 8 to 9 kDa, and the calcium binding capacity was linearly correlated with carboxyl group content (R(2)= 0.8204). FTIR experiments revealed that upon binding calcium, the amide I band underwent a shift to lower wave numbers. A wide, intense Ca-O absorption band also appeared between 400 and 100 cm(-1) in the far-infrared spectrum. The width and intensity of this band increased after treatment of samples with glutaminase. The amount of bound calcium was related to both the molecular weight of the peptides and to the carboxyl group content, and the most likely sites for calcium binding are the carboxyl groups of Asp and Glu.
authors.affiliation: College of Food Science and Nutrition Engineering, China Agricultural University, 17 Qinghua Road, Haidian District, Beijing 100083, PRC.
authors.forename: X-L
authors.initials: XL
authors.lastname: Bao
authors.forename: Y
authors.initials: Y
authors.lastname: Lv
authors.forename: B-C
authors.initials: BC
authors.lastname: Yang
authors.forename: C-G
authors.initials: CG
authors.lastname: Ren
authors.forename: S-T
authors.initials: ST
authors.lastname: Guo
mesh_terms: D000327:Adsorption; D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D002850:Chromatography, Gel / Q000379:methods; D010450:Endopeptidases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007610:Kallikreins / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism; D008970:Molecular Weight; D010434:Pepsin A / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D011485:Protein Binding; D011492:Protein Hydrolysates; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry* / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
chemical_list: D011492:Protein Hydrolysates; D030262:Soybean Proteins; D010450:Endopeptidases; D010447:Peptide Hydrolases; C412470:flavourzyme; C103551:KLK6 protein, human; D007610:Kallikreins; D010434:Pepsin A; D008666:Metalloendopeptidases; C044194:microbial metalloproteinases; D002118:Calcium