Biosynthesis of trimethylamine oxide in calanoid copepods. seasonal changes in trimethylamine monooxygenase activity

Live copepods, Calanus finmarchicus (Gunnerus) and C. hyperboreus (Krøyer), exposed to dissolved ¹⁴C-labeled trimethylamine (TMA) in seawater, oxidized TMA to trimethylamine oxide (TMAO), which accumulated in the organisms. The amount of TMAO synthesized was dependent on the time of exposure to TMA and the concentration of TMA in the seawater. It was inferred that copepods can produce TMAO by oxidation of TMA found in their plant food. Choline and methionine did not appear to be of importance as precursors of TMAO. There were large seasonal changes in TMA monooxygenase activity of both copepods. The activity was high in spring, and decreased through summer and autumn to a winter low in October to March. The changes in TMAO content of C. finmarchicus were, in comparison, small (this aspect was not tested for C. hyperboreus).