TABLE 5.

Effects of EDTA and calcium ions on the solvent-induced in vitro isomerization of unsaturated fatty acids of crude membranes from Pseudomonas and E. coli cells^a

Membrane sourceb	EDTA (5 mM)	CaCl2 (30 mM)	% Conversion to trans-9-hexadecenoic acidc
P. oleovorans GPo12	−	−	60
P. oleovorans GPo12	+	−	12
P. oleovorans GPo12	+	+	53
E. coli AM1095	−	−	56
E. coli AM1095	+	−	9
E. coli AM1095	+	+	49

^aCrude membranes of P. oleovorans GPo12 or wild-type E. coli AM1095 which contained 0.5 μmol of cis-9-hexadecenoic acid were incubated with 0.01 U of cis-trans isomerase, 0.1% (vol/vol) octanol, and various amounts of EDTA and CaCl₂ in a final assay volume of 0.5 ml (phosphate buffer [50 mM, pH 7.2]). After 60 min of incubation, an aliquot (0.1 ml) of the assay solution was removed to determine fatty acid composition. To the residual assay solution CaCl₂ was added, and after an additional 60 min of incubation the fatty acids were analyzed. Each value is the average of three independent experiments. 

^bCrude membranes were isolated from spheroplasts of P. oleovorans GPo12 and E. coli AM1095 as described in Materials and Methods. 

^cThe in vitro isomerization of membranes was expressed as the percentage of trans-9-hexadecenoic acid relative to the total amount of cis-9-hexadecenoic acid and trans-9-hexadecenoic acid.