SOME FACTORS INVOLVED IN TRIMETHYLAMINE N-OXIDE (TMAO) DEMETHYLATION IN POST MORTEM RED HAKE MUSCLE

The pH optimum for demethylation of TMAO in minced red hake muscle at –5C was approximately 7.0. This value was higher than the pH optimum for the crude soluble enzyme in an anaerobic system utilizing flavin and NADH and for an aerobic system with ferric iron and ascorbate but was similar to the pH optimum observed with the flavin-NADH system in the presence of air. Both the anaerobic and aerobic flavin-NADH systems had sufficient activity in the presence of optimal concentrations of cofactors to account for all of the demethylation of TMAO observed in minced muscle. Comparison of concentrations of flavins and NADH and their rate of change during storage at temperatures both below and above freezing with previously determined kinetic constants suggest that this cofactor system may be critical in determining the rate of TMAO demethylation in post mortem red hake muscle. The extent of TMAO breakdown at –5C caused by the iron-ascorbate system was barely sufficient to account for the amount of DMA produced in the minced muscle. With the relatively low concentrations of iron and ascorbate present in the tissue, this system seems unlikely to be a major factor in TMAO degradation in situ.