ENANTIOSELECTIVE OXIDATION BY NONHEME IRON MONO-OXYGENASES FROM PSEUDOMONAS

Xylene oxygenase (XO), an enzyme system from Pseudomonas putida mt-2, selectively oxidizes the methyl side group of toluene-derived compound s. The enzyme is related to Pseudomonas oleovorans mono-oxygenase (POM ), which has been used to produce optically active epoxides from vario us alkenes at high enantiomeric excess. We have introduced XO into Esc herichia coli and produced variously substituted benzyl alcohols from toluene derivatives and optically active styrene epoxides from styrene , m- and p-chlorostyrene and m- and p-methylstyrene using this biocata lyst. The products of oxidation of styrene and styrene derivatives had enantiomeric excesses (ees) ranging from 37% to over 98%. Similarly, Pseudomonas putida was engineered such that the hydroxylation of compo unds by POM could be investigated independent of subsequent product de gradation. The biocatalyst accepted a wide range of substrates and oxi dized both linear and branched alkanes, and cyclic alkanes as well as alkylbenzenes to the corresponding alcohols. In this review we describ e the catalytic potential of engineered biocatalysts based on both XO and POM and discuss the structural and functional similarities of thes e non-heme iron monooxygenases.