Enhancing effect of Fe2+ on the formaldehyde production from trimethylamine N-oxide decomposition catalyzed by the extract of Harpadon nehereus kidney

The effects of Fe²⁺ on the trimethylamine N-oxide (TMAO) demethylating activity of the Harpadon nehereus kidney extract were studied in this research. The activity of the kidney extract was presumably inhibited by ethylene diamine tetra-acetic acid (EDTA), which indicates that the kidney extract contains an enzyme or enzyme system with metal cations as activator. Activity of the kidney extract was enhanced significantly when Fe²⁺ was added into the model system in vitro. As the concentration of Fe²⁺ increased, the decomposing rate of TMAO increased rapidly until TMAO decomposed completely. The activity of the kidney extract was also enhanced by reductant such as ascorbic acid. Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) was employed to determine the content of total iron in a number of fishery products. Significant positive correlation between the contents of total iron and endogenous formaldehyde (FA) was found, especially in marine products.