Tetralin as a Substrate for Camphor (Cytochrome P450) 5-Monooxygenase

Author： Grayson D.A. Tewari Y.B. Mayhew M.P. Vilker V.L. Goldberg R.N.

Publisher： Elsevier

ISSN： 0003-9861

Source： Archives of Biochemistry and Biophysics, Vol.332, Iss.2, 1996-08, pp. : 239-247

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Abstract

Camphor (cytochrome P450) 5-monooxygenase, originally isolated from the bacterium Pseudomonas putida PgG 786, catalyzes the essentially stereospecific conversion of tetralin (1,2,3,4-tetrahydronaphthalene) to ( R )-1-tetralol (( R )-(-)-1,2,3,4-tetrahydro-1-naphthol): tetralin(aq) + NADH(aq) + O 2 (aq) = ( R )-1-tetralol(aq) + NAD(aq) + H 2 O(l). The ratio of the amount of ( S )-1-tetralol to the amount of ( R )-1-tetralol is small (~0.04) and the reaction is essentially stereospecific. The reaction time-course plot indicates the formation of additional product(s) from the ( R )-1-tetralol. It is found that the above reaction obeys Michaelis-Menten kinetics and that dimethyl sulfoxide, methanol, and p -dioxane serve as accelerators. Approximate values of a Michaelis constant K m , limiting rate V max , and catalytic constant k cat are obtained for this reaction under a specified set of conditions. It is shown by means of a thermochemical cycle calculation that the apparent equilibrium constant for this reaction is ~4 x 10 65 at T = 298.15 K and pH 7.3. Thus, this reaction is "irreversible" and, unless the enzyme system is inactivated, it will proceed in the direction of complete formation of 1-tetralol from tetralin. A detailed description of the preparation of the camphor (cytochrome P450) 5-monooxygenase enzyme system from recombinant microorganisms is given.