Different Acyl Acceptors

Du, W., Xu, Y., Liu, D., and Zeng, J. 2004. Comparative study on lipase-catalyzed transformation of soybean oil for biodiesel production with different acyl acceptors. J. Mol. Catal. B Enzym., 3,125-129. 

Du, W., Y. Xu, D. Liu, and J. Zeng. 2004. Comparative Study on Lipase-Catalyzed Transformation of Soybean Oil for Biodiesel Production with Different Acyl Acceptors. Journal of Molecular Catalysis B Enzymatic 30 (3-4) 125-129. 

A stepwise addition of methanol was the most common strategy to avoid lipase inactivation (Chen et al., 2009). Using a different acyl acceptor as methyl acetate or ethyl acetate, the lipase inactivation is also avoided (Jeong and Park, 2010). Another strategy for solving the problem of Upase inactivation by methanol is the use of organic solvents (Iso et al., 2001), but difficulties in solvent recovery make these methods less competitive at an industrial scale. 

A combinatorial approach for biocatalytic production of polyesters was demonstrated. A library of polyesters were synthesized in 96 deep-well plates from a combination of divinyl esters and glycols with lipases of different origin. In this screening, lipase CA was confirmed to be the most active biocatalyst for the polyester production. As acyl acceptor, 2,2,2-trifluoroethyl esters and vinyl esters were examined and the former produced the polymer of higher molecular weight. Various monomers such as carbohydrates, nucleic acids, and a natural steroid diol were used as acyl acceptor. 

The unexpected formation of cyclopenta[b]indole 3-339 and cyclohepta[b]indole derivatives has been observed by Bennasar and coworkers when a mixture of 2-in-dolylselenoester 3-333 and different alkene acceptors (e. g., 3-335) was subjected to nonreductive radical conditions (hexabutylditin, benzene, irradiation or TTMSS, AIBN) [132]. The process can be explained by considering the initial formation of acyl radical 3-334, which carries out an intermolecular radical addition onto the alkene 3-335, generating intermediate 3-336 (Scheme 3.81). Subsequent 5-erafo-trig cyclization leads to the formation of indoline radical 3-337, which finally is oxidized via an unknown mechanism (the involvement of AIBN with 3-338 as intermediate is proposed) to give the indole derivative 3-339. 

Bile acids are also conjugated by a similar sequence of reactions involving a microsomal bile acid CoA ligase and a soluble bile acid A-acyl-transferase. The latter has been extensively purified, and differences in acceptor amino acids, of which taurine is the most common, have been related to the evolutionary history of the species. 

According to this proposal, the incorporation of proline into collagen follows the acyl adenylate and acyl RNA stages now generally believed to occur in protein synthesis. A bound hydroxyproline intermediate is postulated, from which hydroxyproline is transferred to soluble RNA. We prefer to suggest that different RNA acceptor molecules exist for hydroxyproline and proline this would be consistent with recent work which indicates that the soluble RNA molecule contains the information for incorporation of a particular amino acid into protein (3). Although it is conceivable that there is hydroxylation of prolyl-sRNA to yield hydroxyprolyl-sRNA, an additional mechanism would be needed... 

Du et al. (6) have recently reported that methyl acetate was an effective acyl acceptor for biodiesel production. To the best of our knowledge, the biodiesel production from waste edible oil with methyl acetate as the acyl acceptor has not yet been reported. Therefore, the transesterification of different kinds of waste edible oil to biodiesel with methyl acetate in a solvent free system was explored in this paper and the major influential factor on the reaction was further investigated. 

In 1998 So, et al. [43] screened 15 different commercial lipases for the synthesis of dipeptides from D-amino acids, and found only PPL to be effective. They also found certain amino acids to be better acyl acceptors, and L-isomers of the same D-amino acids showed similar reactivity for peptide synthesis, but the D-isomers resulted in better yields. 

For glyceraldehyde-3-phosphate dehydrogenase, conflicting conclusions have been reached by different workers (47 49). From one analysis of initial rate data, for the pig muscle enzyme, it appears that with glycer-aldehyde as substrate the mechanism is random (SO), whereas with glyceraldehyde 3-phosphate there is random combination of this substrate and NAD followed by phosphate as the compulsory third substrate (48). On the other hand, inhibition studies with the rabbit muscle enzyme indicate an ordered mechanism in which NAD is the first and acyl acceptor the last substrate to combine (51). More detailed comparative initial rate studies with the several aldehydes w hich act as substrates (Section II,E), preferably by a fluorimetric method (11,47), and isotope exchange studies at equilibrium are needed for this enzyme. 

Levels of the Molecular Species of [ " QPC. The levels of incorporation of various [ " C]FA into the molecular species of [ " C]PC in castor microsomal incubations (60 min) are shown in Table 3. The [ " C]PC were derived primarily from the action of acyl-CoA /y5oPC acyltransferase with endogenous lysoVC as acyl acceptor. The lyso C could contain one of the six different FA in the sn- position, and the [ " C]FA at sn-2 were from [ " C]acyl-CoA. In general, the levels of the FA in the sn- position of [ " C]PC were in the order of linoleate > palmitate > oleate > linolenate, stearate and ricinoleate, with linoleate and palmitate as the major sn-l components of PC. This order, then, reflects the... 

The Friedel-Crafts alkylation is one of the oldest synthetic methodologies known. The catalytic asymmetric version of the reaction [311] enables the preparation of important chiral building blocks. Electron-rich aromatic and heteroaromatic compounds have been productively used in organocatalyzed enantioselective inter- and intramolecular Friedel-Craft-[312] type conjugate additions over different Michael acceptors such as, a,p-unsaturated aldehydes, a,P-unsaturated ketones, nitroole-fins, and a,p-unsaturated acyl phosphonates. 

In contrast to the G3P-AT, the mitochondrial LPA-ATs from the two different organs displayed very similar properties. Both enzymes did not show a fatty acid specificity with respect to the acyl groups in the acyl acceptor, but they showed one with respect to the acyl groups in the acyl donor. 

Preparation of MAGs using Upases is currently weU known and can occur via several different routes (Hayes, 2004 Watanabe and Shimada, 2009). [In addition to glycerol, other glycols can serve as acyl acceptor for the preparation of bio-based surfactants (Hayes, 2004).] Key aspects for bioprocessing are the need to enable miscibility between acyl donor and glycerol substrates and retain low water concentrations for reactions involving ester bond formation, to increase the yield of ester upon the approach of thermodynamic... 

Alcohols are the most frequently used acyl acceptors, particularly methanol and, to a lesser extent, ethanol. Other alcohols can be used, eg, propanol, butanol, isopropanol, ferf-butanol, branched alcohols, and octanol, but the cost is much higher. Regarding the choice between methanol and ethanol, the former is cheaper, more reactive, and the fatty acid methyl esters (FAME) are more volatile than those of the fatty acid ethyl esters (FAEE). However, ethanol is less toxic and it can be considered more renewable because it can be easily produced from renewable sources by fermentation of agricultural feedstocks. In contrast, methanol is mainly produced from nonrenewable fossil sources, such as natural gas. Methanol also inhibits Upases. Regarding their characteristics as fuels, FAME and FAEE show very sUght differences (Demirbas, 2008). 

Thus, the ratio of methanol to oil is a critical parameter in optimization studies. Various lipases have shown a different level of tolerance toward methanol. Most of the researchers have optimized the methanol to oil molar ratio in the range of 3 1 to 4 1 for lipase-catalyzed conversion. Some lipases have shown optimum activity at higher methanol to oil ratio. To overcome methanol inhibition, various alternatives have been suggested by researchers, including stepwise addition of methanol, the use of other acyl acceptors, use of solvent, and use of methanol-tolerant lipase (Kumari et al., 2007 CamUo Naranjo et al., 2010). 

Biofuels similar to biodiesel produced using several acyl acceptors, different to methanol... 

The high competitive strength of an alcohol was demonstrated by the transesterification of 1-phenyl ethyl butyrate with octanol as the acyl acceptor in an emulsion system [22]. Addition of a water-miscible solvent, which extracts the alcohol from the interface, can increase the enantiomeric excess of the product. This effect was observed in several different systems [23-25]. 

Table 10 includes the results for skin irritation. No clear results have been obtained. All models are in agreement only for the absence of irritative potential of BDE 100. Multiple results from ToxTree are due to the five different alerts used by the model (Schiff base formation, SNAr, Acyl transfer agent, skin sensitization, and Michael acceptor). A global evaluation of ToxTree data could suggest that all the analyzed compounds are not able to induce skin sensitization. These predictions are in clear contrast with that obtained by applying CAESAR and in partial agreement with the results of Toxsuite. 

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