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김시욱,임헌만,신현재,김희곤,Yan Kim 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.4
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 55oC, respectively. The Vmax and Km 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 W3A1.
Methylovorus sp. strain SS1 DSM 11726의 메탄올 대사와 세포외 다당류 생합성
김재성,김시욱,김영민,Kim, Jae. S.,Kim, Si W.,Kim, Young M. 한국미생물학회 1998 미생물학회지 Vol.34 No.4
메탄올을 이용하여 성장하는 Methylovorus sp. strain SS1은 formaldehyde의 산화를 위한 linear route의 주효소인 $NAD^+$-linked formaldehyde dehydrogenase 및 $NAD^+$-linked formate dehydrogenas와 cyclic route의 주효소인 hexulose-6-phosphate synthase, glucose-6-phosphate isomerae, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase 등의 활성을 나타내었는데, cyclic route에 관여하는 효소의 활성이 상대적으로 더 높았다. 이 세균은 formaldehyde의 동화와 관련된 ribulose monophosphate 경로의 주효소와 Entner-Doudoroff 경로의 주효소 및 transaldolase 활성과 함께 세포외 다당류 합성과 관련된 phosphoglucomutase, UDP-glucose pyrophyosphorylase, mannose-6-phosphate isomerase의 활성도 나타내었다. 2.3 mM의 ammonium sulfate가 포함된 배지에서 성장한 세균은 7.6 mM의 ammonium sulfate가 포함된 배지에서 성장한 세균보다 더 많은 세포외 다당류를 생산하였지만 균체 수율은 낮았고, 6-phosphogluconate dehydrogenase와 phosphoglucomutase 및 UDP-glucose pyrophoshorylase의 활성은 높게 나타내었으나 6-phosphogluconate dehydratase/2-keto-3-deoxy-6-phosphogluconate aldolase의 활성은 낮았다. Melhylovorus sp. strain SS1 grown on methanol was found to show activities of key enzymes of the linear route, $NAD^+$-linked formaldehyde and formate dehydrogenases, and the cyclic route, hexulose-6-phosphate synthase, glucose-6-phosphate isomerase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase, for formaldehyde oxidation. The activities of the cyclic route enzymes were higher than those of the linear route enzymes. The bacterium also exhibited activities of the key enzymes of the ribulose monophosphate and Entner-Doudoroff pathways and transaldolase involved in the formaldehyde assimilation and the enzymes involved in the biosynthesis of extracellular polysaccharide. Cells grown in the presence of 2.3 mM ammonium sulfate were higher in the productivity of extracellular polysaccharide, but lower in the growth yield, than those grown in the presence 7.6 mM ammonium sulfate. The activities of 6-phosphogluconate dehydrogenase, phosphoglucomutase, and UDP-pyrophosphorylase in cells grown under nitrogen-limited condition were higher, but that of 6-phosphogluconate dehydratase/2-keto-3-deoxy-6-phosphogluconate aldolase was lower, than those in cells grown in the presence of sufficient amount of nitrogen source.