Stereochemical aspects of the oxidation of 4-ethylphenol by the bacterial enzyme 4-ethylphenol methylenehydroxylase.
The O2-independent hydroxylase 4-ethylphenol methylenehydroxylase (4EPMH) from Pseudomonas putida JD1 catalysed the complete conversion of 4-ethylphenol into 1-(4-hydroxyphenyl)ethanol together with a small amount of 4-hydroxyacetophenone, but with no formation of the side product 4-vinylphenol reported to be formed when the similar enzyme p-cresol methylhydroxylase (PCMH) catalyses this reaction. The enantiomer of 1-(4-hydroxyphenyl)ethanol produced by 4EPMH was R(+) when horse heart cytochrome c or azurin was used as electron acceptor for the enzyme. PCMHs from various bacterial strains produced the S(-)-alcohol. Both enantiomers of 1-(4-hydroxyphenyl)ethanol were substrates for conversion into 4-hydroxyacetophenone by 4EPMH, but the S(-)-isomer was preferred. The Km and kcat. were 1.2 mM and 41 s-1 respectively for the S(-)-alcohol and 4.7 mM and 22 s-1 for the R(+)-alcohol. In addition to the 1-(4-hydroxyphenyl)ethanol dehydrogenase activity of 4-EPMH, NAD(+)-linked dehydrogenase activity for both enantiomers of the alcohol was found in extracts of Ps. putida JD1.
Department of Biochemistry, University College of Wales, Aberystwyth, U.K.
C D
CD
Reeve
M A
MA
Carver
D J
DJ
Hopper
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010636:Phenols / Q000378:metabolism*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology; D013237:Stereoisomerism
D001426:Bacterial Proteins; D010636:Phenols; C011867:4-hydroxyphenylethanol; C042291:4-ethylphenol; D006899:Mixed Function Oxygenases; D000429:Alcohol Oxidoreductases; C062024:4-ethylphenol methylenehydroxylase; D010626:Phenylethyl Alcohol