Benzylic monooxygenation catalyzed by toluene dioxygenase from Pseudomonas putida

Abstract

Toluene dioxygenase, a multicomponent enzyme system known to oxidize mononuclear aromatic hydrocarbons to cis-dihydrodiols, oxidized indene and indan to 1-indenol and 1-indanol, respectively. In addition, the enzyme catalyzed dioxygen addition to the nonaromatic double bond of indene to form cis-1,2-indandiol. The oxygen atoms in 1-indenol and cis-1,2-indandiol were shown to be derived from molecular oxygen, whereas 70% of the oxygen in 1-indanol was derived from water. All of the isolated products were optically active as demonstrated by 19F NMR and HPLC discrimination of diastereomeric esters and by chiroptic methods. The high optical purity of (-)-(1R)-indanol (84% enantiomeric excess) and the failure of scavengers of reactive oxygen species to inhibit the monooxygenation reaction supported the contention that the monooxygen insertion is mediated by an active-site process. Experiments with 3-[2H]indene indicated that equilibration between C-1 and C-3 occurred prior to the formation of the carbon-oxygen bond to yield 1-indenol. Naphthalene dioxygenase also oxidized indan to 1-indanol, which suggested that benzylic monoxygenation may be typical of this group of dioxygenases.

Degradation of fluorene by Brevibacterium sp. strain DPO 1361: a novel C-C bond cleavage mechanism via 1,10-dihydro-1,10-dihydroxyfluoren-9-one

“…Therefore, the actual formation of fluorenol is probably due to a monooxygenation mode of a dioxygenase, as described above for the cloned dioxygenase of P. stutzeri AN 10. This finding is also consistent with several reports on monooxygenation reactions which are catalyzed by dioxygenases (25,29,33,34,36). 9-Fluorenol thus formed is then converted to 9-fluorenone by a dehydrogenase that is strongly induced during growth on fluorene but not after growth with DBF or biphenyl.…”

Actions of a versatile fluorene-degrading bacterial isolate on polycyclic aromatic compounds?

“…A number of studies have shown that certain arene dioxygenases act as monooxygenases and hydroxylate the benzylic functions of naphthenoaromatic compounds. The resultant secondary alcohols serve as substrates for dehydrogenases to yield the corresponding ketones (6,45,52 acenaphthoquinone as a dead-end product. In a recent work (45) P. aeruginosa PAO1, carrying the naphthalene dioxygenase genes cloned from the naphthalene plasmid NAH7, mono-oxygenated acenaphthene to 1-acenaphthenol and then to a mixture of cisand trans-acenaphthene diols, which were transformed to acenaphtenone and acenaphtoquinone by the action of nonspecific dehydrogenases.…”

“…These studies have yielded fundamental information about the biodegradability of individual compounds, but little is known of the fate of those compounds in mixtures. It has been recognized that a number of aromatic hydrocarbon degraders have the ability to transform other aromatic substrates to various extents (9,14,15,30,31,33,44,45,47,52,53), suggesting that biotransformations may play important roles in the degradation of environmental mixtures. A number of studies document the degradation of PAC mixtures.…”

Oxidation of aliphatic olefins by toluene dioxygenase: enzyme rates and product identification

“…TDO is a versatile enzyme, mechanistically. It can catalyze monooxygenation (23,31), desaturation (28), O dealkylation (22), N dealkylation (12), sulfoxidation (12), and oxidative dehalogenation (14,30) reactions.…”