Chelation of calcium ions by poly(γ-glutamic acid) from bacillus subtilis (chungkookjang)

摘要

Many studies have clarified that poly(γ-glutamic acid) (PGA) increases the solubility of Ca~(2+), suggesting that PGA enhances calcium absorption in the small intestine. However, there has been no report on the specific interaction between PGA and Ca~(2+) in water. We studied the aqueous solution properties of PGA calcium salt (PGA-Ca complex). The chelating ability and binding strength of PGA for Ca~(2+) were evaluated. The PGA-Ca complex was soluble in water, in contrast to the insolubility of poly(acrylic acid) (PAA) calcium salt, and the chelating ability of PGA for Ca~(2+) was almost the same as that of PAA. The globular conformation of the PGA-Ca complex in water was estimated by SEC and viscosity measurements. The chelation ability of PGA for Ca~(2+) was examined by ~1H NMR. The present study showing the characteristics of the PGA-Ca complex will provide useful information about the calcium absorption by PGA in vivo.