• Biotechnology and Bioprocess Engineering:BBE
• /
• v.11 no.4
• /
• pp.337-343
• /
• 2006

Trimethylamine dehydrogenase (TMADH, EC 1.5.99.7), an iron-sulfur flavoprotein that catalyzes the oxidative demethylation of trimethylamine to form dimethylamine and formaldehyde, was purified from Methylophaga sp. strain SK1. The active TMADH was purified 12.3-fold through three purification steps. The optimal pH and temperature for enzyme activity was determined to be 8.5 and $55^{\circ}C$, respectively. The $V_{max}\;and\;K_m$ values were 7.9 nmol/min/mg protein and 1.5 mM. A genomic DNA of 2,983 bp from Methylophaga sp. strain SK1 was cloned, and DNA sequencing revealed the open reading frame (ORF) of the gene coding for TMADH. The ORF contained 728 amino acids with extensive identity (82%) to that of Methylophilus methylotrophus $W_3A_1$.

• Journal of Microbiology
• /
• v.43 no.6
• /
• pp.499-502
• /
• 2005

Methylophaga sp. strain SK1 is a new restricted facultative methanol-oxidizing bacterium that was isolated from seawater. The aim of this study was to characterize the electron carriers involved in the methanol oxidation process in Methylophaga sp. strain SK1. The gene encoding cytochrome $c_L$ (mxaG) was cloned and the recombinant gene was expressed in Escherichia coli $DH5\alpha$ under strict anaerobic conditions. The recombinant cytochrome $c_L$ had the same molecular weight and absorption spectra as the wild-type cytochrome $c_L$ both in the reduced and oxidized forms. The electron flow rate from methanol dehydrogenase (MDH) to the recombinant cytochrome $c_L$ was similar to that from MDH to the wild-type cytochrome $c_L$. These results suggest that recombinant cytochrome $c_L$ acts as a physiological primary electron acceptor for MDH.