Fe(III)-{N-(2,3-dihydroxybenzoyl)-L-seryl-[N-(C-5-[deoxy-beta-D-glucosyl]-2,3-dihydroxybenzoyl)-L-serine]2} + H2O + H(+) = Fe(III)-[N-(C-5-[deoxy-beta-D-glucosyl]-2,3-dihydroxybenzoyl)-L-serine]2 + N-(2,3-dihydroxybenzoyl)-L-serine — reaction