- Purification and characterization of OleA from Xanthomonas campestris and demonstration of a non-decarboxylative claisen condensation reaction
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OleA catalyzes the condensation of fatty acyl groups in the first step of bacterial long-chain olefin biosynthesis, but the mechanism of the condensation reaction is controversial. In this study, OleA from Xanthomonas campestris was expressed in Escherichia coli and purified to homogeneity. The purified protein was shown to be active with fatty acyl-CoA substrates that ranged from C 8 to C16 in length. With limiting myristoyl-CoA (C 14), 1 mol of the free coenzyme A was released/mol of myristoyl-CoA consumed. Using [14C]myristoyl-CoA, the other products were identified as myristic acid, 2-myristoylmyristic acid, and 14-heptacosanone. 2-Myristoylmyristic acid was indicated to be the physiologically relevant product of OleA in several ways. First, 2-myristoylmyristic acid was the major condensed product in short incubations, but over time, it decreased with the concomitant increase of 14-heptacosanone. Second, synthetic 2-myristoylmyristic acid showed similar decarboxylation kinetics in the absence of OleA. Third, 2-myristoylmyristic acid was shown to be reactive with purified OleC and OleD to generate the olefin 14-heptacosene, a product seen in previous in vivo studies. The decarboxylation product, 14-heptacosanone, did not react with OleC and OleD to produce any demonstrable product. Substantial hydrolysis of fatty acyl-CoA substrates to the corresponding fatty acids was observed, but it is currently unclear if this occurs in vivo. In total, these data are consistent with OleA catalyzing a non-decarboxylative Claisen condensation reactionin the first step of the olefin biosynthetic pathway previously found to be presentin at least 70 different bacterial strains.
- Frias, Janice A.,Richman, Jack E.,Erickson, Jasmine S.,Wackett, Lawrence P.
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scheme or table
p. 10930 - 10938
(2012/03/26)
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- Infrared, X-ray diffraction studies and thermogravimetric behaviour of magnesium myristate and magnesium palmitate
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Magnesium soaps i.e., magnesium myristate and magnesium palmitate were prepared by the metathesis of potassium soaps with an aqueous solution of magnesium sulphate. The infrared results showed that the fatty acid exists in a dimeric structure as a result of hydrogen bonding between the carboxyl groups of two acid molecules, whereas magnesium soaps have an ionic character. The X-ray diffraction analysis indicates that the zig-zag chains of fatty acid radical constituent of the soap molecules extend straight forward on both sides of each basal plane. The thermal decomposition of these soaps was found kinetically of zero order and energy of activation for the decomposition process was in the range of 15-32 KJ mol-1.
- Singh, Chitra,Upadhyaya
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body text
p. 3011 - 3013
(2012/02/02)
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- Catalytic conversion of C12-C14 primary alcohols mixture into long-chain ketones
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A charge of raw primary alcohols of high molecular weight from commercial plant was transformed into long-chain ketones fraction of potential commercial use. In this continuous flow method LaMnO3/La-Al2O 3 catalyst was used. At 420 °C and a normal pressure mixture of 74.2 wt.% C12 and 25.8 wt.% C14 primary alcohols and toluene (weight ratio alcohols:toluene = 1:1) was converted into ketones with 73.4% yield in relation to the theoretical value. Ketones were analyzed by TLC, NMR and GC-MSD.
- Klimkiewicz, Roman,Morawski, Ireneusz,Trawczyński, Janusz
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experimental part
p. 1143 - 1147
(2010/11/16)
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