Trenz S P, Engesser K H, Fischer P, Knackmuss H J
Institut für Mikrobiologie, Stuttgart, Germany.
J Bacteriol. 1994 Feb;176(3):789-95. doi: 10.1128/jb.176.3.789-795.1994.
Angular dioxygenation has been established as the crucial step in dibenzofuran degradation by Brevibacterium sp. strain DPO 1361 (V. Strubel, K. H. Engesser, P. Fischer, and H.-J. Knackmuss, J. Bacteriol. 173:1932-1937, 1991). The same strain utilizes biphenyl and fluorene as sole sources of carbon and energy. The fluorene degradation sequence is proposed to be initiated by oxidation of the fluorene methylene group to 9-fluorenol. Cells grown on fluorene exhibit pronounced 9-fluorenol dehydrogenase activity. Angular dioxygenation of the 9-fluorenone thus formed yields 1,10-dihydro-1,10-dihydroxyfluoren-9-one (DDF). A mechanistic model is presented for the subsequent C-C bond cleavage by an NAD(+)-dependent DDF dehydrogenase, acting on the angular dihydrodiol. This enzyme was purified and characterized as a tetramer of four identical 40-kDa subunits. The following Km values were determined: 13 microM for DDF and 65 microM for 2,3-dihydro-2,3-dihydroxybiphenyl. The enzyme also catalyzes the production of 3-(2'-carboxyphenyl)catechol, which was isolated, and structurally characterized, in the form of the corresponding lactone, 4-hydroxydibenzo-(b,d)-pyran-6-one. Stoichiometry analysis unequivocally demonstrates that angular dioxygenation constitutes the principal pathway in Brevibacterium sp. strain DPO 1361.
角双加氧作用已被确认为短杆菌属菌株DPO 1361降解二苯并呋喃的关键步骤（V. Strubel、K. H. Engesser、P. Fischer和H.-J. Knackmuss，《细菌学杂志》173:1932 - 1937，1991年）。同一菌株利用联苯和芴作为唯一的碳源和能源。芴的降解序列被认为是从芴亚甲基氧化为9 - 芴醇开始的。在芴上生长的细胞表现出显著的9 - 芴醇脱氢酶活性。由此形成的9 - 芴酮的角双加氧作用产生1,10 - 二氢 - 1,10 - 二羟基芴 - 9 - 酮（DDF）。本文提出了一个作用于角二氢二醇的NAD(+)依赖性DDF脱氢酶进行后续C - C键裂解的机制模型。该酶被纯化并鉴定为四个相同的40 kDa亚基组成的四聚体。测定了以下Km值：DDF为13 μM，2,3 - 二氢 - 2,3 - 二羟基联苯为65 μM。该酶还催化生成3 - (2'-羧基苯基)邻苯二酚，其以相应内酯4 - 羟基二苯并-(b,d)-吡喃 - 6 - 酮的形式被分离并进行了结构表征。化学计量分析明确表明，角双加氧作用是短杆菌属菌株DPO 1361中的主要途径。
