Purification and Properties of Trimethylamine N-Oxide Reductase from Shewanella sp. NCMB 400

Abstract

Two major trimethylamine-N-oxide reductases were detected in the periplasmic fraction of the marine bacterium Shewanella sp. NCMB 400 grown in the presence of trimethylamine N-oxide (TMAO). The high-M r enzyme was purified to homogeneity and consisted of a single polypeptide of M r 86000 as judged by SDS-PAGE. The second enzyme had an M r of 47000. On isoelectric focusing, multiple forms of the purified enzyme were revealed with isoelectric points of 5·1 and 5·2. The K m values for the N-oxides of trimethylamine, pyridine and γ-picoline were 0·02, 2·41 and 6·95 mm, respectively. The purified TMAO reductase is a molybdoenzyme containing 1·32 mol Mo (mol enzyme)−1.