Zahn J A, Bergmann D J, Boyd J M, Kunz R C, DiSpirito A A
Department of Microbiology, Iowa State University, 205 Science Building, Ames, IA 50011, USA.
J Bacteriol. 2001 Dec;183(23):6832-40. doi: 10.1128/JB.183.23.6832-6840.2001.
A membrane-associated, dye-linked formaldehyde dehydrogenase (DL-FalDH) was isolated from the obligate methylotroph Methylococcus capsulatus Bath. The enzyme was the major formaldehyde-oxidizing enzyme in cells cultured in high (above 1 micromol of Cu per mg of cell protein) copper medium and expressing the membrane-associated methane monooxygenase. Soluble NAD(P)(+)-linked formaldehyde oxidation was the major activity in cells cultured in low-copper medium and expressing the soluble methane monooxygenase (Tate and Dalton, Microbiology 145:159-167, 1999; Vorholt et al., J. Bacteriol. 180:5351-5356, 1998). The membrane-associated enzyme is a homotetramer with a subunit molecular mass of 49,500 Da. UV-visible absorption, electron paramagnetic resonance, and electrospray mass spectrometry suggest the redox cofactor of the DL-FalDH is pyrroloquinoline quinone (PQQ), with a PQQ-to-subunit stochiometry of approximately 1:1. The enzyme was specific for formaldehyde, oxidizing formaldehyde to formate, and utilized the cytochrome b(559/569) complex as the physiological electron acceptor.
从专性甲基营养菌荚膜甲基球菌巴斯德菌株中分离出一种与膜相关的、染料连接的甲醛脱氢酶（DL-FalDH）。该酶是在高铜（每毫克细胞蛋白中铜含量高于1微摩尔）培养基中培养并表达与膜相关的甲烷单加氧酶的细胞中的主要甲醛氧化酶。在低铜培养基中培养并表达可溶性甲烷单加氧酶的细胞中，可溶性NAD(P)(+)连接的甲醛氧化是主要活性（泰特和道尔顿，《微生物学》145:159 - 167，1999；福尔霍尔特等人，《细菌学杂志》180:5351 - 5356，1998）。这种与膜相关的酶是一种同四聚体，亚基分子量为49,500道尔顿。紫外可见吸收、电子顺磁共振和电喷雾质谱表明，DL-FalDH的氧化还原辅因子是吡咯喹啉醌（PQQ），PQQ与亚基的化学计量比约为1:1。该酶对甲醛具有特异性，将甲醛氧化为甲酸，并利用细胞色素b(559/569)复合物作为生理电子受体。
