Cereal Chem 52:21 - 33.  |  VIEW ARTICLE
Binding of Ca(II) by the 11S Fraction of Soybean Proteins.

A. G. Appurao and M. S. Narasinga Rao. Copyright 1975 by the American Association of Cereal Chemists, Inc. 

Binding of Ca(II) by the 11S fraction of soybean proteins was determined by equilibrium dialysis at pH 7.8 and 5.5. The binding was negligible at pH 5.5. At pH 7.8 binding was decreased by the addition of 0.5M NaCl. Prior treatment with EDTA also reduced the binding. Analysis of the binding data with the Scatchard equation suggested that the probable binding site on the protein molecules was the imidazole group. Addition of Ca(II) did not cause association or dissociation of the protein. Heat coagulation was increased by the addition of Ca(II). The protein was almost quantitatively precipitated at 1.0 x 10(-2)M Ca(II). This precipitation was decreased by the addition of NaCl. Binding studies with the unfractionated soybean proteins indicated that Ca(II) was bound by the proteins as well as the phytate impurities. When these were removed Ca(II) appeared to be bound by the proteins at the imidazole group.