Ralstonia sp. U2 naphthalene dioxygenase and Comamonas sp. JS765 nitrobenzene dioxygenase show differences in activity towards methylated naphthalenes.
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.
Department of Biotechnology, SINTEF Materials and Chemistry, 7465 Trondheim, Norway. Anne.Tondervik@sintef.no
Anne
A
Tøndervik
Per
P
Bruheim
Laila
L
Berg
Trond E
TE
Ellingsen
Hans K
HK
Kotlar
Svein
S
Valla
Mimmi
M
Throne-Holst
D020585:Comamonas / Q000201:enzymology*; D049308:Dioxygenases / Q000737:chemistry / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009281:Naphthalenes / Q000378:metabolism*; D009578:Nitrobenzenes / Q000378:metabolism; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism; D043367:Ralstonia / Q000201:enzymology*; D013379:Substrate Specificity
D009097:Multienzyme Complexes; D009281:Naphthalenes; D009578:Nitrobenzenes; C031969:1,4-dimethylnaphthalene; C036077:nitrobenzene; C025968:1-methylnaphthalene; D010105:Oxygenases; D049308:Dioxygenases; C038703:naphthalene dioxygenase