Characterization of a Pseudomonas putida allylic alcohol dehydrogenase induced by growth on 2-methyl-3-buten-2-ol

We have been working to develop an enzymatic assay for the alcohol 2-methyl -3-buten-2-ol (232-MB), which is produced and emitted by certain pines. To this end we have isolated the soil bacterium Pseudomonas putida MB-1, which uses 232-MB as a sole carbon source, Strain MB-1 contains inducible 3-meth yl-2-buten-1-ol (321-MB) and 3-methyl-2-buten-1-al dehydrogenases, suggesti ng that 232-MB is metabolized by isomerization to 321-MB followed by oxidat ion, 321-MB dehydrogenase was purified to near-homogeneity and found to be a tetramer (151 kDa) with a subunit mass of 37,700 Da. It catalyzes NAD(+)- dependent, reversible oxidation of 321-MB to 3-methyl-2-buten-1-al. The opt imum pH for the oxidation reaction was 10.0, while that for the reduction r eaction was 5.4, 321-MB dehydrogenase oxidized a wide variety of aliphatic and aromatic alcohols but exhibited the highest catalytic specificity with allylic or benzylic substrates, including 321-MB, 3-chloro-2-buten-1-ol, an d 3-aminobenzyl alcohol. The N-terminal sequence of the. enzyme contained a region of 64% identity with the TOL plasmid-encoded benzyl alcohol dehydro genase of P. putida. The latter enzyme and the chromosomally encoded benzyl alcohol dehydrogenase of Acinetobacter calcoaceticus were also found to ca talyze 321-MB oxidation. These findings suggest that 321-MB dehydrogenase a nd other bacterial benzyl alcohol dehydrogenases are broad-specificity ally lic and benzylic alcohol dehydrogenases that, in conjunction with a 232-MB isomerase, might be useful in an enzyme-linked assay for 232-MB.