Saturated hydrocarbons enzymic hydroxylations

Moreover, the slight differences in reactivity of C—H bonds in alkanes to free radicals lead to indiscriminate attack of the hydrocarbon chains. Improvements in the efficiency and selectivity in the conversion of saturated hydrocarbons under relatively mild conditions is a desirable goal. This objective may be achieved by the selective activation of C—H bonds in alkanes by the use of suitable metal catalysts. The latter condition obtains in the selective microbiological hydroxylation of saturated hydrocarbons (see Section V.A), in which the enzyme probably interacts with the hydrocarbon via metal-catalyzed redox reactions. 

According to a widely accepted consensus, the complexation of 02 with heme followed by the two-step electron transition leads to the formation of the state [Fe2+02"], in which the dioxygen adopts an active form capable of hydroxylating the substrates, including saturated hydrocarbons (Coon et. al., 1981 Guengerich and Macdonald 1984). The complexation and the first electron transfer proceed rapidly and take place at atmospheric pressure of dioxygen froml0"2to 10 3s. The second electron transfer is a relatively slow reaction (for the enzyme from P. Putida, k = 4 s 1), which commonly limits the entire process. 

A bacterial mediane noonooxygenase that catalyzes the hydroxylation of saturated hydrocarbons has been isolated, but there are severe limitations in practical use. Similarly the enzymes involved in steroid hydroxylation have been isolated and used in but this practice is not sufficiently well... 

The hydroxylation activity of the P.450 enzyme is very important, for example, in deioxiftcation pathways. Some bioraimetic reactions have been studied in connection with this problem and, in fact, they contribuie 10 the understanding of the effects acting at the enzyme catalytic site. For example, Mimoun [54] reported on the smooth hydroylation of saturated hydrocarbons... 

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