Department of Biotechnology, SINTEF Materials and Chemistry, 7465 Trondheim, Norway.
J Biosci Bioeng. 2012 Feb;113(2):173-8. doi: 10.1016/j.jbiosc.2011.10.001. Epub 2011 Oct 28.
Methylsubstituted naphthalenes constitute a significant part of light gas oil fractions (LGO). These are toxic compounds with low fuel value, and can potentially be enzymatically modified to increase the fuel value and at the same time reduce toxicity. The first step in the biodegradation of naphthalene involves dioxygenation of the aromatic ring catalysed by naphthalene dioxygenase (NDO). Here we show that recombinantly produced NDO from Ralstonia sp. U2 and the related nitrobenzene dioxygenase (NBDO) from Comamonas sp. JS765 can use several mono-, di-, tri-, and tetramethylated naphthalenes as substrates. For the majority of the substrates both enzymes catalyse the formation of a mixture of mono- and dioxygenated products, and it is only dioxygenated products that are likely to be processed further, leading to ring cleavage. In some cases, like for 1-methylnaphthalene, NDO mainly generates the monooxygenated form, while with NBDO, the dioxygenated form dominates. In other cases, as for 1,4-dimethylnaphthalene, the monooxygenated product dominates with NDO, whereas NBDO generates similar amounts of both forms. Presumably, the best future strategy for bioconversion of methylated naphthalenes in LGO is to develop engineered enzyme that are optimised with respect to the specific composition of naphthalene derivatives found in a given product.
甲基取代的萘构成了轻质瓦斯油馏分（LGO）的重要组成部分。这些是有毒化合物，燃料值低，并且可以通过酶法修饰来提高燃料值，同时降低毒性。萘的生物降解的第一步涉及萘双加氧酶（NDO）催化的芳香环的双氧化。在这里，我们展示了重组来自 Ralstonia sp. U2 的 NDO 和相关的来自 Comamonas sp. JS765 的硝基苯双加氧酶（NBDO）可以用作几种单、二、三、四甲基萘的底物。对于大多数底物，两种酶都催化形成单加氧和双氧化产物的混合物，只有双氧化产物可能进一步被处理，导致环裂解。在某些情况下，如 1-甲基萘，NDO 主要生成单加氧产物，而 NBDO 则以双氧化产物为主。在其他情况下，如 1,4-二甲基萘，NDO 生成的单加氧产物占优势，而 NBDO 则生成两种形式的产物。推测，在 LGO 中生物转化甲基萘的最佳未来策略是开发针对特定产品中发现的萘衍生物组成进行优化的工程化酶。
