TMAOase, trimethylamine-N-oxide demethylase, is a thermostable and active enzyme at 80°C

Purified trimethylamine-N-oxide demethylase (TMAOase) from walleye pollack muscle is a thermostable protein that was not inactivated after heating at 80degreesC for 30 min. The heated enzyme was electrophoresed in the same manner as for native enzyme. Circular dichroism (CD) spectra for purified enzyme changed reversibly in the temperature range of 10-80degreesC. As the enzyme was still active at 80degreesC, the CD spectral change did not directly relate to enzyme activity. TMAOase activity in the myofibrillar fraction decreased sharply above 30degreesC, but was extracted and recovered from the heated myofibrillar fraction, suggesting that the activity seemed to be interrupted and apparently inactivated due to the thermal alteration of myofibrillar proteins or some unknown factors. The complicated profile found in dimethylamine (DMA) formation from trimethylamine-N-oxide (TMAO) in walleye pollack muscle during heating consisted of both enzymic and non-enzymic processes. Most DMA was produced enzymatically below 40degreesC and interrupted above 40degreesC. Therefore, DMA and trimethylamine was formed non-enzymatically at high temperatures regardless of the presence of native enzyme. A new, simple and easy purification method was proposed based on the thermostable nature of the enzyme.