Regiospecific effect of 1-octanol on cis-trans isomerization of unsaturated fatty acids in the solvent-tolerant strain Pseudomonas putida S12

The solvent-tolerant bacterium Pseudomonas putida S12, which adapts its mem brane lipids to the presence of toxic solvents by a cis to trans isomerizat ion of unsaturated fatty acids, was used to study possible in vivo regiospe cificity of the isomerase. Cells were supplemented with linoleic acid (C18: 2 Delta9-cis,Delta 12-cis), a fatty acid that cannot be synthesized by this bacterium, but which was incorporated into membrane lipids up to an amount of 15% of total fatty acids. After addition of I-octanol, which was used a s an activator of the cis-trans isomerase, the linoleic acid was converted into the Delta9-trans,Delta 12-cis isomer, while the Delta9-cis,Delta 12-tr ans and Delta9-trans,Delta 12-trans isomers were not synthesized. Thus, for the first time, regiospecific in vivo formation of novel, mixed cis/trans isomers of dienoic fatty acid chains was observed. The maximal conversion ( 27-36% of the chains) was obtained at 0.03-0.04% (v/v) octanol, after 2 h. The observed regiospecificity of the enzyme, which is located in the peripl asmic space, could be due to penetration of the enzyme to a specific depth in the membrane as well as to specific molecular recognition of the substra te molecules.