Redox enzyme mediated biocatalysis has the potential to regio - and stereo-specificity oxidive hydrocarbons producing valuable products with minimal by-product formation. In-vitro reactions of the Camphor (cytochrome P-450) 5-monooxygenase enzyme system with naphthalene-like substrates yield stereospecifically hydroxylated products from nonactivated hydrocarbons. Specifically, the enzyme system catalyzes the essentially stereospecific conversion of the cycloarene, tetralin (1,2,3,4-tetrahydronaphthalene) to (R)-1-tetralol ((R)-(-)-1,2,3,4-tetrahydro-1-naphthol). It is shown that this reaction obeys Michaelis-Menten kinetics and that the interactions between the enzyme subunits are not affected by the identity of the substrate. This subunit independence extends to the efficiency of NADH usage by the enzyme system -- subunit ratios do not affect efficiency, but substrate identity does. Tetralin is converted at an efficiency of 13 3%, whereas (R)-1-tetralol is converted at 7.8 0.7%. A model of this system based on Michaelis-Menten parameters for one subunit (Pdx: KM = 10.2 2 M and both substrates (tetralin: KM = 66 26 M, Ņmax = 0.11 0.04 s-1; and (R)-1-tetralol: KM = 2800 1300 M, Ņmax = 0.83 0.22 s-1) is presented and used to predict the consumption and production of all substrates, products, and cofactors.
Citation: Journal of Molecular Catalysis B-Enzymatic
Pub Type: Journals
chiral biosynthesis, cytovchrome P450, tetralin