Synthesis of fatty acid anhydrides by reaction with dicyclohexylcarbodiimide

A simple method is described for the preparation of caprylic, palmitic, stearic, and oleic anhydrides. Reaction of the free fatty acid and dicyclohexylcarbodiimide in carbon tetrachloride at room temperature gives the corresponding anhydrides in high yield (87-94%).     

Lipases in organic solvents: The fatty acid chain length profile

Summary Competitive lipase-catalysed hydrolyses of triacylglycerols were used for the quantitative determination of the fatty acid profile of several lipases. In contrast to previously described methods a complete and reliable activity profile for triacylglycerols containing fatty acid residues with chain lengths from C₄ to C₁₈₁ can be obtained in one single experiment.     

Equilibration of alditol anhydrides in acetic acid

Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4. Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups. Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are also proposed as intermediates in the structural isomerisation. Drastic treatment of each alditol gives equilibrium mixtures. The equilibrium concentrations are used to calculate free-energy differences.     

Enantioselectivity of the hydrolysis of linoleic acid monoepoxides catalyzed by soybean fatty acid epoxide hydrolase.

Soybean epoxide hydrolase efficiently catalyzes the hydration of the two positional isomers of linoleic acid monoepoxides into their corresponding vic-diols. Kinetic analysis of the progress curves, obtained at low substrate concentrations (i.e. [So] much less than Km), and analysis of the residual substrates by chiral-phase HPLC, indicate that the hydrolase is highly enantioselective, i.e. cis-9R,10S-epoxy-12(Z)-octadecenoic and cis-12R,13S-epoxy-9(Z)-octadecenoic acids are preferentially hydrolyzed (the enantioselectivity ratios are 15 and 28, respectively). Importantly, these two enantiomers are the one formed preponderantly by epoxidation of linoleic acid by peroxygenase, a hydroperoxide-dependent oxidase we have previously described in soybean (Blée, E., and Schuber, F., Biochem. Biophys. Res. Commun. (1990) 173, 1354-1360).     

Dicarboxylic acid anhydrides as dissociating agents of protein-containing structures

Dissociation of protein-containing structures by modification of protein amino groups with dicarboxylic acid anhydrides is a mild procedure which, in some cases, offers advantages over treatment with alternative dissociating agents, such as urea, guanidine hydrochloride, detergents, high ionic strength, and extremes of pH: In addition to dissociating multimeric proteins and protein aggregates, dicarboxylic acid anhydrides are effective dissociating agents for membrane-bound proteins and nucleoprotein particles. With most dicarboxylic acid anhydrides reviewed, the introduced reagent residues can be eliminated under moderate acid conditions, which allows the purification of unmodified individual components, and the use of disassembly-reconstitution systems valuable for investigating the structural and functional roles played by the individual components of complex particles:Each reagent can be suitable for a particular purpose, depending on the required specificity of the modification and stability of the modified groups: The stability of the acylated amino groups ranges from the very stable succinylated amino groups to the very labile acylation obtained with dimethylmaleic anhydride: Between these extremes, the stability of the modified amino groups decreases stepwise in the following order: maleic, exo-cis-3,6-endoxo-⁴-tetrahydrophthalic, citraconic, and 3,4,5,6-tetrahydrophthalic anhydride. With respect to the selectivity of the produced modification, little or no modification of hydroxyamino acid and cysteine residues has been observed with dimethylmaleic, exo-cis-3,6-endoxo-⁴-tetrahydrophthalic, and 3,4,5,6-tetrahydrophthalic anhydrides: With the other reagents, the extent of modification of hydroxyamino acid residues increases in the order citraconic, maleic and succinic anhydride: Citraconic and maleic anhydrides can produce irreversible modification of cysteine residues, the reactivity of sulfhydryl groups being higher with maleic anhydride:     

Stepwise synthesis of oligopeptides with N-carboxy alpha-amino acid anhydrides

Oligopeptides were synthesized in high yields by the controlled coupling reaction of N-carboxy α-amino acid anhydrides (NCA's) with amino acid and peptide sodium salts in the heterogeneous reaction medium of acetonitrile–water which contained sodium carbonate. In this solvent, it could be considered that the reaction could occur at the interface of acetonitrile and aqueous layers, and that NCA's could be protected by the organic layer from side reactions such as hydrolysis and polymerization. The careful control of reaction conditions such as pH of the solution was not necessary when the heterogeneous mixed solvent was used. Sodium carbonate which had not been used for a reaction of this kind could be satisfactorily used for stabilizing the carbamate intermediates in the aqueous layer of the heterogeneous reaction medium.     

Identification of N-acylethanolamines in Dictyostelium discoideum and confirmation of their hydrolysis by fatty acid amide hydrolase

N-acylethanolamines (NAEs) are endogenous lipid-based signaling molecules best known for their role in the endocannabinoid system in mammals, but they are also known to play roles in signaling pathways in plants. The regulation of NAEs in vivo is partly accomplished by the enzyme fatty acid amide hydrolase (FAAH), which hydrolyses NAEs to ethanolamine and their corresponding fatty acid. Inhibition of FAAH has been shown to increase the levels of NAEs in vivo and to produce desirable phenotypes. This has led to the development of pharmaceutical-based therapies for a variety of conditions targeting FAAH. Recently, our group identified a functional FAAH homolog in Dictyostelium discoideum, leading to our hypothesis that D. discoideum also possesses NAEs. In this study, we provide a further characterization of FAAH and identify NAEs in D. discoideum for the first time. We also demonstrate the ability to modulate their levels in vivo through the use of a semispecific FAAH inhibitor and confirm that these NAEs are FAAH substrates through in vitro studies. We believe the demonstration of the in vivo modulation of NAE levels suggests that D. discoideum could be a good simple model organism in which to study NAE-mediated signaling.     

Lysophospholipid and fatty acid inhibition of pulmonary surfactant: non-enzymatic models of phospholipase A2 surfactant hydrolysis

Secretory A(2) phospholipases (sPLA(2)) hydrolyze surfactant phospholipids cause surfactant dysfunction and are elevated in lung inflammation. Phospholipase-mediated surfactant hydrolysis may disrupt surfactant function by generation of lysophospholipids and free fatty acids and/or depletion of native phospholipids. In this study, we quantitatively assessed multiple mechanisms of sPLA(2)-mediated surfactant dysfunction using non-enzymatic models including supplementation of surfactants with exogenous lysophospholipids and free fatty acids. Our data demonstrated lysophospholipids at levels >or=10 mol% of total phospholipid (i.e., >or=10% hydrolysis) led to a significant increase in minimum surface tension and increased the time to achieve a normal minimum surface tension. Lysophospholipid inhibition of surfactant function was independent of the lysophospholipid head group or total phospholipid concentration. Free fatty acids (palmitic acid, oleic acid) alone had little effect on minimum surface tension, but did increase the maximum surface tension and the time to achieve normal minimum surface tension. The combined effect of equimolar free fatty acids and lysophospholipids was not different from the effect of lysophospholipids alone for any measurement of surfactant function. Surfactant proteins did not change the percent lysophospholipids required to increase minimum surface tension. As a mechanism that causes surfactant dysfunction, depletion of native phospholipids required much greater change (equivalent to >80% hydrolysis) than generation of lysophospholipids. In summary, generation of lysophospholipids is the principal mechanism of phospholipase-mediated surfactant injury in our non-enzymatic models. These models and findings will assist in understanding more complex in vitro and in vivo studies of phospholipase-mediated surfactant injury.     

Ultrasonic-pretreated waste activated sludge hydrolysis and volatile fatty acid accumulation under alkaline conditions: Effect of temperature

The effect of temperature on the hydrolysis and acidification of ultrasonic-pretreated waste activated sludge (WAS) under alkaline conditions was investigated in this study. The experiment temperatures were set at 10, 20, 37, and 55°C. Experimental results showed that the hydrolysis of ultrasonic-pretreated WAS under alkaline conditions increased significantly with temperature from 10 to 55°C, while the volatile fatty acid (VFA) accumulation was not augmented as temperature increased. Among the four temperatures tested, 37°C was the point with the highest VFA accumulation after 72h fermentation. VFA accumulation decreased markedly at 55°C compared to 37°C. Mechanism investigation revealed that among all the temperatures tested, 37°C was the temperature at which consumptions of WAS protein and carbohydrate, activities of key enzymes related to VFA formation and ratio of Bacteria to Archaea all reached the maximum. Due to activities of related microorganisms inhibited by higher temperature (55°C), VFA accumulation decreased at 55°C.