Aromatic hydroxylation catalyzed by toluene 4-monooxygenase in organic solvent/aqueous buffer mixtures.
Toluene 4-monooxygenase is a four-protein component diiron enzyme complex. The enzyme catalyzes the hydroxylation of toluene to give p-cresol with approximately 96% regioselectivity. The performance of the enzyme in two-phase reaction systems consisting of toluene, hexane, or perfluorohexane and an aqueous buffer was tested. In each of the cosolvent systems, containing up to 93% (v/v) of solvent, the enzyme was active and exhibited regioselectivity indistinguishable from the aqueous reaction. Using the perfluorohexane/buffer system, a number of polycyclic aromatic hydrocarbons were oxidized that were not readily oxidized in aqueous buffer. An instability of the hydroxylase component and a substantial uncoupling of NADH utilization and product formation were observed in reactions that were continued for longer than approximately 3 min. More stable enzyme complexes will be needed for broad applicability of this hydroxylating system in nonaqueous media.
Oppenheim
S F
SF
Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Studts
J M
JM
Fox
B G
BG
Dordick
J S
JS
D002021:Buffers; D002384:Catalysis; D002621:Chemistry / Q000379:methods*; D005466:Fluorocarbons / Q000737:chemistry; D006586:Hexanes / Q000737:chemistry; D006900:Hydroxylation; D008956:Models, Chemical; D009243:NAD / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism*; D012995:Solubility; D014050:Toluene / Q000737:chemistry; D014867:Water / Q000737:chemistry
D002021:Buffers; D005466:Fluorocarbons; D006586:Hexanes; D014867:Water; D009243:NAD; D014050:Toluene; D010105:Oxygenases; C068610:toluene-4-monooxygenase; C078626:perflexane