Characterization and role of cis/trans isomerase of unsaturated fatty acids in bacteria.

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Cell-free extract of PseudoNonas sp. strain E-3 catalyzed the conversion of 9cis-hexadecenoib acid[16 : 1(9c)]in a free acid and 16 : 1(9c)esterified to both the sn-1 and 2 positions of phosphatidylethanolamine(PE)to 9-trans-hexadecenoic acid[16 : 1(9t)]. The cell-free extract wa!j separated into the soluble(cytosolic)and membrane fractions by the ultracentrifugation at 105, 000 x g for 60 min. The cytosol fraction catalyzed the isomerization of the free 16 : 1(9c). On the other hand, it isomerized 16 : 1(9c)esterified to PE in the presence of the membrane fraction. One cytosolic component(component I)that catalyze the isomerization of free 16 : 1(9c)and the other(component II)that is needed for the isomerization of esterified 16 : 1(9c)were completely separable one another with a high-performance liquid chromatographic system equipped Kith a gel filtration column. These results suggest that Psedomonas sp. strain E-3 contains at least two types of "Cis/trans isometases.Component I was purified by column chromatography with DEAE-Toyopearl and ButyToyopearl. Purified enzyme was separated into two components by gel-filtration column chromatography. These two components ' were essentially needed for isomeriation of 16 : 1(9c)to 16 : 1(9t). The enzyme has a temperature optimum at ^oC and maintained significant activities at subzero temperatures.