Hydrocarbon-oxidizing enzyme system

Whereas some species oxidize host terpenes more randomly, producing an array of rather unspecific volatiles with little information, others use highly selective enzyme systems for the production of unique olfactory signals. However, apart from transformations of monoterpene hydrocarbons of host trees, oxygenated monoterpenes may well be biosynthesized de novo by the beetles (see below). 

Another source of rubredoxins was found in an aerobic bacterium, Pseudomonas oleovorans, utilizing n-hexane as a carbon source (10). This particular rubredoxin differs from those commonly found in anaerobic bacteria in some of its properties it has a molecular weight of 19,000, and one iron form of the protein is readily converted to a two-iron form (11). The rubredoxin of P. oleovorans functions as a terminal electron transfer component in an enzyme system which participates in the ( -hydroxylation of fatty acids and hydrocarbons. The hydrocarbon-oxidizing... 

Long-term exposure of microbial populations to certain toxicants often is necessary for adaptation of enzymatic systems capable of degrading those toxicants. This was the case with the Exxon Valdez oil spill in Alaska in 1989. Natural microbial populations in Prince William Sound, Alaska, had developed enzyme systems that oxidize petroleum hydrocarbons because of long-term exposure to natural oil seeps and to hydrocarbons that leached from the pine forests in the area. Growth of these natural microbial populations was nutrient limited during the summer. Thus the application of nutrient formulations to the rocky beaches of Prince William Sound stimulated microbial growth and helped to degrade the spilled oil. 

The chemical behavior of 02 after coordination, that is the activation of 02, is a diverse and complex subject because of the many pathways available for 02 reactions. The search for more selective oxidations, especially using 02, is a prime goal that has immense potential on an industrial scale (4, 30), and is thus an important research area. The ultimate aim would be to mimic the 02-activation ability of enzyme systems, for example the ability of cytochrome P 450 to catalyze Reaction 1, where R is a hydrocarbon molecule. 

Various alkane oxidations are catalyzed by iron complexes. Such reactions are important in view of the action of non-heme iron enzymes, such as methane monooxygenase, in hydrocarbon oxidations in biological systems. For example, the oxo-bridged complex [Fe2(TPA)2(ju,-0)(ju.-0Ac)]3+ [TPA = tris(2-pyridylmethyl)-amine] catalyzes the oxidation of cyclohexane with Bu OOH. Related complexes with an Fein2(/i-0)(/i-0Ac)2 core oxidize cyclohexane or adamantane to give a mixture of alcohols and ketones.159 Less well defined systems, e.g., FeCl3-6H20/ aldehyde/AcOH/02 are similarly active.160... 

Carcinogenic hydrocarbons have been reported to increase the activity of this oxidising enzyme system in immature males, adult females and partially hepatectomized adult males [47]. This involves the synthesis of new enzyme protein which may be prevented by ethionine, a competitive antagonist to the incorporation of methionine into new protein [48]. The microsomal enzyme inhibitor SKF 525A similarly prevents oxidation of the phosphoro-thionates, so reducing their toxicity [47], Similar observations on the influence of sex hormones, age and microsomal enzyme inducers on the toxicity of schradan [49, 50], parathion [51, 52], fenitrothion [53], EPN. 0-(4-methyl-7-hydroxycoumarin)-0,( -diethylphosphorothionate (E838) [51] and 0,0-diethyl-0-(3-methyl-4-methylthiophenyl)phosphorothionate (DMP) [54] in rats have been reported. 

A cell-free, soluble enzyme preparation of a Pseudomonad bacterium strain, isolated from soiP", has been found to oxidize octane to n-octanol and octanoic acid. Pyridine nucleotide, oxygen and Fe ions are involved in this bioconversion. The reaction has been studied at 28 °C with a system consisting of buffer, octane(specific activity 5 X lO cpm/imol" ) dissolved in EtOH or acetone, enzyme and suitable cofactors. The reaction could be stopped by the addition of dilute H2SO4. Suitable work-up of the system yielded unreacted " C-octane, " C-octanol and " C-octanoate, respectively. The sum of the radioactivity found in octanol and octanoate served as a measure of the hydrocarbon-oxidizing activity of the enzyme system since the intermediates (hydroperoxide, octanal) do not accumulate. 

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