Determination of binding affinity of poly‐γ‐glutamate to Shiga toxin

We examined poly-γ-glutamate from natto, a Japanese fermented food, in the ability to adsorb Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). The polymer was immobilized by direct coupling to EAH-SepharoseTM. The poly-γ-glutamate-Sepharose (about 10 mg of ligand/mL of gel) adsorbed Stx2, but not Stx1: its dissociation constant (Kd) against Stx2 was calculated to be 14.0 μM. To analyze the binding site of poly-γ-glutamate against Stx2, we similarly immobilized glutamate and glutarate. Glutamate- and glutarate-Sepharoses (each 7 μmol of ligand/mL of gel) similarly adsorbed Stx2, but not Stx1; Kd values against Stx2 were calculated to be 14.0 and 30.0, respectively, μM. The common structures of PGA-, glutamate-, and glutarate-Sepharoses were considered to be glutaryl groups. When we added the mixture of Stx2 and poly-γ-glutamate-Sepharose to Caco-2 cells (a human colon epithelial cell line), poly-γ-glutamate-Sepharose was found to reduce the cytotoxicity of Stx2.

This is the peer reviewed version of the following article: Kanemaru, K, Goto, T, Badr, HA, Yokoigawa, K. Determination of binding affinity of poly‐γ‐glutamate to Shiga toxin. J Food Biochem. 2018; 42:e12538, which has been published in final form at https://doi.org/10.1111/jfbc.12538. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.