Partial purification and characterization of trimethylamine-N-oxide demethylase from lizardfish kidney.

Trimethylamine-N-oxide demethylase (TMAOase) from lizardfish (Saurida micropectoralis) was partially purified by acidification and diethylaminoethyl (DEAE)-cellulose chromatography. The enzyme was purified 82-fold with a yield of 65.4%. The optimum pH and temperature were 7.0 and 50 degrees C, respectively. TMAOase was stable to heat treatment up to 50 degrees C and the activation energy was calculated to be 30.5 kJ mol(-1) K(-1). Combined cofactors (FeCl(2), ascorbate and cysteine) were required for full activation. FeCl(2) exhibited a higher stimulating effect on TMAOase activity than FeCl(3). At concentration less than 2 mM, ascorbate was more stimulatory to the activity than cysteine. The activity was tolerant of NaCl concentration up to 0.5 M. The enzyme had a K(m) for TMAO of 16.2 mM and V(max) of 0.35 micromol min(-1) and was able to convert TMAO to dimethylamine (DMA) and formaldehyde. The molecular mass of enzyme was estimated to be 128 kDa based on activity staining.