Effect of a membrane permeable metal chelator on iron and hemoglobin-mediated lipid oxidation in washed fish muscle

The effect of a membrane permeable metal chelator, N′,N′,N′,N′-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN) on iron and hemoglobin-mediated lipid oxidation in washed cod muscle was evaluated. TPEN stimulated added iron-mediated lipid oxidation in washed cod muscle (pH 6.3) while ethylenediaminetetraacetic acid (EDTA) did not. TPEN delivered iron to cellular membranes of cod muscle more effectively compared to EDTA (p < 0.05). Fe-TPEN remained intact in the presence of excess EDTA which indicated that TPEN had a relatively high affinity for iron. TPEN also promoted lipid hydroperoxide (LOOH) formation in washed cod alone, presumably by chelating and thereby activating endogenous metals. LOOH and hydrogen peroxide formation due to Fe-TPEN may partly explain the observation that TPEN accelerated trout hemoglobin-mediated lipid oxidation in cod muscle. Peroxides accelerate oxidation of hemoglobin (Hb). Oxidized trout Hb readily releases hemin that efficiently decomposes LOOH to free radicals that, in turn, incur oxidation of polyunsaturated fatty acids. These studies indicate that TPEN activates low molecular weight metals that are endogenously present in washed cod and facilitates transport of metals to cellular membranes which exacerbates the ability of hemoglobin to promote lipid oxidation.

► TPEN is a membrane permeable metal chelator. ► TPEN promoted iron and hemoglobin-mediated lipid oxidation in washed cod. ► High affinity of TPEN for Fe(II) in the presence of EDTA was observed. ► TPEN delivered iron to cellular membranes of cod muscle. ► Mechanisms by which TPEN stimulated lipid oxidation in washed cod are discussed.