Fatty acids enzymatic

Most mammalian cells have the capacity to synthesize fatty acids from glucose de novo in a pathway that uses products from glycolysis and two key cytosolic enzymes, acetyl-CoA carboxylase and fatty acid synthase (Chapter 6). This pathway generates long-chain SFA, mainly palmitate (16 0). The de novo synthesized palmitate and the palmitate derived from dietary sources are transported to the ER membranes. In the membranes, two major fatty acid enzymatic modifications of chain elongation and desaturation occur to yield longer chain SFA and unsaturated fatty acids of the n - 9 series. The n - 3 and n - 6 series of PUFA can be synthesized only from dietary fats, as animal cells do not have the... 

Fatty acids are susceptible to oxidative attack and cleavage of the fatty acid chain. As oxidation proceeds, the shorter-chain fatty acids break off and produce progressively higher levels of malodorous material. This condition is known as rancidity. Another source of rancidity in fatty foods is the enzymatic hydrolysis of the fatty acid from the glycerol. The effect of this reaction on nutritional aspects of foods is poorly understood andhttie research has been done in the area. 

Enzymatic acylation reactions offer considerable promise in the synthesis of specific ester derivatives of sucrose. For example, reaction of sucrose with an activated alkyl ester in /V, /V- dim ethyl form am i de in the presence of subtilisin gave 1 -0-butyrylsucrose, which on further treatment with an activated fatty acid ester in acetone in the presence of Hpase C. viscosum produced the 1, 6-diester derivative (71,72). 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

Consumer acceptance of milk is strongly determined by its sensory characteristics. The development of off-flavor in milk as a result of lipolysis can reduce the quality of milk. The enzymatic release, by milk lipase, of free fatty acids (FFA) from triglycerides causes a flavor defect in milk described as rancid . Triglycerides in milk contain both long chain and short chain fatty acids, which are released at random by milk lipase. The short chains FFA, like butyric acid, are responsible for the off-flavor. 

Enzymatically r-BHP, NAPBQI, divicine, fatty acid hydroperoxide ,... 

After the first hydrolytic step, secondary alcohols seem to continue biodegradation through ketone, hydroxyketone, and diketone. Diketones then produce a fatty acid and a linear aldehyde which is further oxidized to fatty acid. Finally, these two fatty acids continue biodegradation by enzymatic 3 oxidation [410],... 

Applications of peroxide formation are underrepresented in chiral synthetic chemistry, most likely owing to the limited stability of such intermediates. Lipoxygenases, as prototype biocatalysts for such reactions, display rather limited substrate specificity. However, interesting functionalizations at allylic positions of unsaturated fatty acids can be realized in high regio- and stereoselectivity, when the enzymatic oxidation is coupled to a chemical or enzymatic reduction process. While early work focused on derivatives of arachidonic acid chemical modifications to the carboxylate moiety are possible, provided that a sufficiently hydrophilic functionality remained. By means of this strategy, chiral diendiols are accessible after hydroperoxide reduction (Scheme 9.12) [103,104]. 

Acetyl-CoA carboxylase is required to convert acetyl-CoA to malonyl-CoA. In turn, fatty acid synthase, a multienzyme complex of one polypeptide chain with seven separate enzymatic activities, catalyzes the assembly of palmitate from one acetyl-CoA and seven malonyl-CoA molecules. 

Epoxide-containing polyesters were enzymatically synthesized via two routes using unsaturated fatty acids as starting substrate (Scheme 11)." Lipase catalysis was used for both polycondensation and epoxidation of unsaturated fatty acid group. One route was synthesis of aliphatic polyesters containing an... 

By the enzymatic esterification of diglycerol with lauric acid, the corresponding monolaurate ester is obtained [84]. This is an important industrial reaction for the cosmetic, pharmaceutical and feed industries, since this ester is used as biodegradable non-ionic surfactant. In recent years, the synthesis of this and other polyglycerols with fatty acids has attracted growing interest in industry, leading also to a demand for enantiomerically and isomerically pure products. 

Chemo-enzymatic epoxidation of unsaturated fatty acids with aqueous H2O2 has been conducted with considerable success and here we have a remarkable situation that undesirable ring opening of the epoxide does not occur. Excellent activity and stability has been realized with Novozym 435, a Candida antartica lipase B immobilized on polyacryl. This enzyme is readily separable, can be used several times without loss of activity, and has a turnover of more than 2,00,000 moles of products per mole of catalyst (Bierman et al., 2000). 

Lipoxygenases catalyse the regio-specific and stereoselective oxygenation of unsaturated fatty acids. The mammalian enzymes have been detected in human platelets, lung, kidney, testes and white blood cells. The leukotrienes, derived from the enzymatic action of the enzyme on arachidonic acid, have effects on neutrophil migration and aggregation, release of lysosomal enzymes, capillary permeability, induction of pain and smooth muscle contraction (Salmon, 1986). 

The stimulus for the recent surge of activity in this previously dormant area of organic chemistry can be traced to the prostaglandin connection . That is to the discovery that saturated bicyclic peroxides are key intermediates in the biosynthesis of prostaglandins and other physiologically active substances by the enzymatic oxygenation of polyunsaturated fatty acids. 

As a reasonable biogenetie pathway for the enzymatic conversion of the polyunsaturated fatty acid 3 into the bicyclic peroxide 4, the free radical mechanism in Equation 3 was postulated 9). That such a free radical process is a viable mechanism has been indicated by model studies in which prostaglandin-like products were obtained from the autoxidation of methyl linolenate 10> and from the treatment of unsaturated lipid hydroperoxides with free radical initiators U). 

Particularly important to the pathways of modular synthases is the incorporation of novel precursors, including nonproteinogenic amino acids in NRP systems [17] and unique CoA thioesters in PK and fatty acid synthases [18]. These building blocks expand the primary metabolism and offer practically unlimited variability applied to natural products. Noteworthy within this context is the contiguous placement of biosynthetic genes for novel precursors within the biosynthetic gene cluster in prokaryotes. Such placement has allowed relatively facile elucidation of biosynthetic pathways and rapid discovery of novel enzyme mechanisms to create such unique building blocks. These new pathways offer a continued expansion of the enzymatic toolbox available for chemical catalysis. 

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