Formation Of Cyclopropane Fatty Acids Research Articles

Competition between cis, trans and Cyclopropane Fatty Acid Formation and its Impact on Membrane Fluidity

AbstractThe impact of cis, trans and cyclopropane fatty acids on membrane fluidity was investigated using batch‐grown Pseudomonas putida P8 and Comamonas testosteroni ATCC 17454. A major difference observed between the two investigated strains is the absence of the ability to synthesize trans‐unsaturated fatty acids in Comamonas. When grown exponentially at 30 °C, a shift to 35 °C increased the trans/cis ratios of the fatty acids of P. putida P8 from 0 to 0.81 and 0 to 1.07, in lipid extracts and cell hydrolyzates, respectively. After prolonged growth followed by nutrient deprivation for 48 h, both at 30 °C, trans fatty acids were absent, but the cyclo/cis ratios rose from 0.1 to 1.55 in lipid extracts, and from 0.1 to 1.54 in cell hydrolyzates. C. testosteroni ATCC 17454 contained no cyclo fatty acids when harvested in the exponential phase after 6 h, whereas after 72 h cultivation, the cyclo/cis ratios rose to 0.49 and 0.47, in lipid extracts and cell hydrolyzates, respectively. Trans fatty acids were never observed in this strain. Increased cyclo/cis and trans/cis ratios correlated with decreased fluidity measured by the fluorescence anisotropy of 1,6‐diphenyl‐1,3,5‐hexatriene (DPH) intercalated in the bilayers of liposomes and by Fourier Transform Infrared (FTIR) spectroscopy of lipids prepared from the cells. The specific effect of cyclopropane fatty acids on membrane fluidity was much smaller than that of trans fatty acids. FTIR‐measurements of intact cells of P. putida P8 confirmed the high potency of trans fatty acids to decrease the fluidity. In cells with induced cyclopropane fatty acid synthesis, the membranes remained more fluidized, indicating the lower importance of these fatty acids for homeoviscosis.

Temperature- and growth-phase-regulated changes in lipid fatty acid structures of psychrotolerant groundwater Proteobacteria.

Cellular fatty acid compositions of five psychrotolerant groundwater isolates representing alpha- and beta-Proteobacteria were studied at temperatures ranging from 8 to 25 degrees C. Unsaturation of straight-chain fatty acids was the most common response to decreasing temperature and was detected in four of the isolates. On solid media, decrease of temperature resulted in a decrease of cyclopropane fatty acids in beta-proteobacterial isolates. The formation of cyclopropane fatty acids depended, however, to a greater extent on the growth phase than the temperature and increased drastically as the cells entered stationary phase. The alpha-proteobacterial isolates contained a branched C(19:1) fatty acid. The formation of the branched C(19:1) increased during growth in the same way as the cyclopropane fatty acids in beta-proteobacterial strains, indicating possibly an analogous formation of the branched fatty acid by methylation of the 18:1 fatty acid. Sphingomonas sp. K6 possessed a novel temperature-induced modification of lipid fatty acids. As temperature decreased from 25 to 8 degrees C, the fatty acid composition shifted from predominantly even-carbon fatty acids to odd-carbon fatty acids. The results show completely different fatty acid modifications in two strains of the same genus Sphingomonas.

The growth phase-dependent synthesis of cyclopropane fatty acids in Escherichia coli is the result of an RpoS(KatF)-dependent promoter plus enzyme instability.

The formation of cyclopropane fatty acids (CFAs) in Escherichia coli is a post-synthetic modification of the phospholipid bilayer that occurs predominantly as cultures enter the stationary phase of growth. The mechanism of this growth phase-dependent regulation of CFA synthesis was unclear, since log-phase and stationary-phase cultures had been reported to contain similar levels of the enzyme catalysing the reaction (CFA synthase). We report that the timing of CFA synthesis can be explained by two unusual features. Fist, the gene encoding CFA synthase (cfa) was found to be transcribed from two promoters and the 5' ends of both transcripts were mapped by primer extension. One of the promoters was active only during the log-to-stationary phase transition and depended on the putative sigma factor encoded by the rpoS(katF) gene whereas the other promoter had a standard sigma 70 promoter consensus sequence and was expressed throughout the growth curve. Second, CFA synthase activity was shown to be unstable in vivo and a Cfa fusion protein was found to have a half life of < 5 min. The combination of these factors meant that, although CFA synthase was synthesized throughout the growth curve, a large increase in activity occurred during the log-to-stationary phase transition. As stationary phase progressed, the increased CFA synthase activity rapidly declined to the basal level. This transient increase in CFA synthase activity coupled with the cessation of net phospholipid synthesis in stationary phase provides an explanation for the unusual time course of CFA synthesis.

Relationship between cyclopropane synthetase and the formation of cyclopropane fatty acids by Proteus vulgaris grown under various respiratory conditions.

In medium saturated with oxygen, the cyclopropane synthetase (unsaturated-phospholipid methyltransferase; EC 2.1.1.16) of Proteus vulgaris was generally synthesized after the mid-exponential phase of growth. The enzyme could also be induced by rapidly limiting the oxygen supply, or by initiating respiration on nitrate or thiosulphate following an initial period of growth in a highly aerobic environment. In each of these 'step-down' situations the specific activity of cyclopropane synthetase rose to a maximum prior to the stationary phase of growth and subsequently decreased. The cyclopropane fatty acids, methylene hexadecanoic acid and methylene octadecanoic acid accumulated throughout exponential growth following the induction of the enzyme. During a 12 h period in the stationary phase there was little synthesis of either of the fatty acids, despite detectable cyclopropane synthetase activity in the cells, indicating that essentially all the fatty acid synthesis was complete prior to entering the stationary phase. When nitrate was used as a respiratory electron acceptors a twofold increase in octadecenoic acid was observed, giving rise to an increase in methylene octadecanoic acid. This increase in octadecanoic acid was not apparent in mutants unable to respire on nitrate.

Augmentation of Cyclopropane Fatty Acid Synthesis under Stringent Control in &lt;italic&gt;Escherichia coli&lt;/italic&gt;&lt;xref ref-type="fn" rid="fn1"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/xref&gt;&lt;xref ref-type="fn" rid="fn2"&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/xref&gt;

An abrupt increase of cyclopropane fatty acid (CFA) occurred concomitant with a decrease of the corresponding unsaturated fatty acids in CP78 (rel+) of Escherichia coli at the onset of the stationary growth phase, whereas such variations were slight in CP79 (rel-). When the cells were starved for isoleucine, the CFA content increased in CP78 but not in CP79. The rate of 14C-incorporation from [methyl-14C]methionine into CFAs increased in CP78 abut two-fold due to the starvation. The apparent level of CFA synthase also increased due to the starvation. These results that the CFA formation is augmented under stringent control.

Properties and biosynthesis of cyclopropane fatty acids in Escherichia coli

The lipid phase transition of Escherichia coli phospholipids containing cyclopropane fatty acids was compared with the otherwise homologous phospholipids lacking cyclopropane fatty acids. The phase transitions (determined by scanning calorimetry) of the two preparations were essentially identical. Infection of E. coli with phage T3 inhibited cyclopropane fatty acid formation over 98%, whereas infection with mutants which lack the phage coded S-adenosylmethionine cleavage enzyme had no effect on cyclopropane fatty acid synthesis. These data indicate that S-adenosylmethionine is the methylene in cyclopropane fatty acid synthesis.

Studies on the biosynthesis of cyclopropane fatty acids in Escherichia coli

By use of various mutants either defective in unsaturated fatty acid biosynthesis or altered in the level of S-adenosylmethionine we have tested the effects of changes in the intracellular concentrations of these substrates on in vivo cyclopropane fatty acid synthesis. A 1.5-fold change in unsaturated fatty acid content produced an equivalent change in cyclopropane fatty acid content. A 20-fold difference in S-adenosylmethionine content had little or no effect on cyclopropane fatty acid formation. Studies with unsaturated fatty acid auxotrophs showed that unsaturated fatty acid synthesis is not required for cyclopropane fatty acid synthesis. Other studies demonstrated that cyclopropane fatty acid content had little effect on phospholipid stability. Finally, we have shown by three methods (gas-liquid chromatography, proton and 15C nuclear magnetic resonance spectra) that the cyclopropane ring of these Escherichia coli acids has the cis configuration.

Relation between Cyclopropane Fatty Acid Formation and Saturation of Phospholipid Species in Escherichia coli K-12

Alterations in the degrees of saturation of phosphatidylethanolamine, phosphatidylglycerol and cardiolipin of Escherichia coli K–12 were determined after raising or lowering the growth temperature during the exponential growth phase. After raising the growth temperature from 17 to 42°C, the cells continued to grow with increasing degrees of saturation of the three phospholipids. cis-9,10-Methylenehexadecanoic acid increased only in phosphatidylethanolamine. During growth after lowering the growth temperature from 42 to 17°C, no increase was found in cyclopropane fatty acid content of phosphatidylethanolamine, in which cis-vaccenic acid increased. Significance of cyclopropane fatty acid formation in phospholipids was discussed.

The path of hydrogen in the formation of cyclopropane fatty acids

The path of hydrogen in the formation of cyclopropane fatty acids

The path of hydrogen in the formation of cyclopropane fatty acids

The path of hydrogen in the formation of cyclopropane fatty acids