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Biosynthesis of Fatty Acids - AOCS Lipid Library

T1 - Fatty acid biosynthesis in Ehrlich cells. The mechanism of short term control by exogenous free fatty acids

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[Mechanism of biosynthesis of fatty acids]. - …

Based on protein architecture, FASs are classified as type I or type II. The type II FAS consists of a dissociated system formed by a discrete and highly conserved group of enzymes encoded by a series of separate genes (). This system has been characterized from bacteria and parasites as well as mitochondria and chloroplasts (the site of fatty acid biosynthesis in plants), where it catalyses de novo fatty acid synthesis (except in mycolic acid producers), usually from acetyl-CoA (; ). The classical type I FAS consists of a multifunctional protein carrying all the catalytic domains on a single polypeptide chain (). These enzymes are typically found in eukaryotes () (though not in plants) and as a remarkable prokaryotic exception in the mycolic acid-producing actinomycetes (). FAS I enzymes can be subdivided according to their domain arrangements and oligomerization state. Microbial type I FASs consist of a single type of polypeptide organised as a hexamer (α6) (; ), with a different domain order compared to the vertebrate FAS (). Mycobacteria and corynebacteria type I FASs are hexamers with a domain arrangement of: acyltransferase, enoyl reductase, dehydratase, malonyl/palmitoyl transferase, acyl carrier protein, 3-ketoacyl reductase and 3-ketoacyl synthase (AT-ER-DH-MPT-ACP-KR-KS), an organization that differs from that of the animal FAS (KS-AT-DH-ER-KR-ACP-TE) (). Besides, animal FAS releases free fatty acids by hydrolytic cleavage catalyzed by a thioesterase (TE) domain (), while the type I FASs of yeast, mycobacteria and corynebacteria use an integral malonyl/palmitoyl transferase activity (MPT) for transacylation of palmitate (or any other end acyl-enzyme product) from the enzyme to CoA (; ).

T1 - Fatty acids and immune responses - A new perspective in searching for clues to mechanism

All organisms that produce fatty acids do so via a repeated cycle of reactions. In mammals and other animals, these reactions are catalyzed by a type I fatty acid synthase (FAS), a large multifunctional protein to which the growing chain is covalently attached. In contrast, most bacteria (and plants) contain a type II system in which each reaction is catalyzed by a discrete protein. The pathway of fatty acid biosynthesis in Escherichia coli is well established and has provided a foundation for elucidating the type II FAS pathways in other bacteria (). However, fatty acid biosynthesis is more diverse in the phylum Actinobacteria: Mycobacterium, possess both FAS systems while Streptomyces species have only the multi-enzyme FAS II system and Corynebacterium species exclusively FAS I. In this review we present an overview of the genome organization, biochemical properties and physiological relevance of the two FAS systems in the three genera of actinomycetes mentioned above. We also address in detail the biochemical and structural properties of the acyl-CoA carboxylases (ACCases) that catalyzes the first committed step of fatty acid synthesis in actinomycetes, and discuss the molecular bases of their substrate specificity and the structure-based identification of new ACCase inhibitors with anti-mycobacterial properties.

mechanism; fatty acid synthase; fatty acids;

The seed oil of a Papaveraceae was shown to contain about 1% of 9-keto- and 11-keto-octacosanoic acids, and a 30 carbon chain keto fatty acid, 11-keto-triacontanoic acid ().

The isolation and structure elucidation of an unusual fatty acid with g-oxocrotonate partial structure have been described ().

One motivation to present a comprehensive and comparative review of fatty acid biosynthesis in these three genera of actinomycetes was to focus on the remarkable differences between them in the content of their membrane and storage lipid components and consequently on the lipid biosynthetic machinery. Even though streptomycetes undergo a complex life cycle with distinctive developmental and morphological stages (), the cell wall is similar to that of other Gram-positive bacteria, composed of a simple peptidoglycan mesh surrounding the cytoplasmic membrane. By contrast, the cell walls of Mycobacterium spp., as well as species of related genera including Corynebacterium, Gordonia, Nocardia, and Rhodococcus, are formed by a thick meso-diaminopimelic acid-containing peptidoglycan covalently linked to arabinogalactan, which in turn is esterified by long-chain α-alkyl, β-hydroxy fatty acids called mycolic acids (). While in mycobacteria these fatty acids have very long carbon chains (C60–90) and may contain various oxygen functions in addition to the β-hydroxyl group (), mycolic acids found in other actinomycetes consist of a mixture of saturated and unsaturated fatty acids with shorter carborn chains like C22–36 in corynomycolic acids (; ). Mycolic acids are believed to play a central role in the formation of a second permeability barrier functionally similar to the outer membrane in Gram-negative bacteria (; ). While the latter is a typical bilayer of phospholipid and lipopolysaccharide, in mycobacteria and corynebacteria it consists of a monolayer of mycoloyl residues covalently linked to the cell-wall arabinogalactan, to form mycoloyl arabinogalactan (MAG), or acylated to trehalose units fo form trehalose monomycolate (TMM) and trehalose dimycolate (TDM) (; ) (). Besides mycolic acids, the outer membrane of mycobacteria also contains an array of very complex lipids relevant in the infection process of the pathogenic mycobacteria, such as dimycocerosate esters (DIMs), sulpholipids and mycoketides (; ; ). In the last few years cell-free reconstitution studies demonstrated that several of these compounds are synthesized from acyl-CoA molecules, most probably derived from the fatty acid biosynthesis pathway, which are further elongated by specific FAS related enzymes known as polyketide synthases (PKS) (; ; ).

Biosynthesis of Fatty Acids: ..

Cholesterol is an important lipid in higher organisms, and its concentration must be maintained in narrow limits depending of the cell needs. An excess of dietary cholesterol can lead to serious health problems, however, if consumption of this lipid is restricted in the diet, cells have the capacity to synthesize it. For the synthesis of cholesterol, the cell uses a family of proteins named sterol regulatory element binding proteins (SREBP's), that are transcriptional factors involved in the control of expression of genes of cholesterol and fatty acids synthesis. SREBP's regulate gene transcription by binding to cis-acting elements denominated sterol regulatory elements (SRE-1). SREBP's are localized in the endoplasmic reticulum, but in the event that the cell needs to synthesize cholesterol, the NH2-terminal portion of these proteins is cleaved by two specific proteases, and then travels into the nucleus to function as transcriptional factor. The present review shows the details of the mechanism that the cell uses to regulate cholesterol biosynthesis by the SREBP's, and its potential metabolic implications.

The trypanosome variant surface glycoprotein (VSG) is anchored to the plasma membrane via a glycosyl phosphatidylinositol (GPI). The GPI is synthesized as a precursor, glycolipid A, that is subsequently linked to the VSG polypeptide. The VSG anchor is unusual, compared with anchors in other cell types, in that its fatty acid moieties are exclusively myristic acid. To investigate the mechanism for myristate specificity we used a cell-free system for GPI biosynthesis. One product of this system, glycolipid A′, is indistinguishable from glycolipid A except that its fatty acids are more hydrophobic than myristate. Glycolipid A′ is converted to glycolipid A through highly specific fatty acid remodeling reactions involving deacylation and subsequent reacylation with myristate. Therefore, myristoylation occurs in the final phase of trypanosome GPI biosynthesis.

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  • Biosynthesis of Fatty acids (from Acetyl CoA) - YouTube

    Production of very long chain polyunsaturated fatty acids in oilseed plants.

  • 21/03/2014 · Biosynthesis of Fatty acids ..

    (2005) Stepwise engineering to produce high yields of very long-chain polyunsaturated fatty acids in plants.

  • Biosynthesis of Saturated Fatty acids Notes - …

    Biosynthesis of Fatty Acids ..

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De novo synthesis of fatty acids (Biosynthesis of fatty acids)

N2 - Cholesterol is an important lipid in higher organisms, and its concentration must be maintained in narrow limits depending of the cell needs. An excess of dietary cholesterol can lead to serious health problems, however, if consumption of this lipid is restricted in the diet, cells have the capacity to synthesize it. For the synthesis of cholesterol, the cell uses a family of proteins named sterol regulatory element binding proteins (SREBP's), that are transcriptional factors involved in the control of expression of genes of cholesterol and fatty acids synthesis. SREBP's regulate gene transcription by binding to cis-acting elements denominated sterol regulatory elements (SRE-1). SREBP's are localized in the endoplasmic reticulum, but in the event that the cell needs to synthesize cholesterol, the NH2-terminal portion of these proteins is cleaved by two specific proteases, and then travels into the nucleus to function as transcriptional factor. The present review shows the details of the mechanism that the cell uses to regulate cholesterol biosynthesis by the SREBP's, and its potential metabolic implications.

19-22-- The Reaction Sequence for the Biosynthesis of Fatty Acids;

N2 - The trypanosome variant surface glycoprotein (VSG) is anchored to the plasma membrane via a glycosyl phosphatidylinositol (GPI). The GPI is synthesized as a precursor, glycolipid A, that is subsequently linked to the VSG polypeptide. The VSG anchor is unusual, compared with anchors in other cell types, in that its fatty acid moieties are exclusively myristic acid. To investigate the mechanism for myristate specificity we used a cell-free system for GPI biosynthesis. One product of this system, glycolipid A′, is indistinguishable from glycolipid A except that its fatty acids are more hydrophobic than myristate. Glycolipid A′ is converted to glycolipid A through highly specific fatty acid remodeling reactions involving deacylation and subsequent reacylation with myristate. Therefore, myristoylation occurs in the final phase of trypanosome GPI biosynthesis.

Fatty acid biosynthesis in Ehrlich cells. The mechanism …

AB - Cholesterol is an important lipid in higher organisms, and its concentration must be maintained in narrow limits depending of the cell needs. An excess of dietary cholesterol can lead to serious health problems, however, if consumption of this lipid is restricted in the diet, cells have the capacity to synthesize it. For the synthesis of cholesterol, the cell uses a family of proteins named sterol regulatory element binding proteins (SREBP's), that are transcriptional factors involved in the control of expression of genes of cholesterol and fatty acids synthesis. SREBP's regulate gene transcription by binding to cis-acting elements denominated sterol regulatory elements (SRE-1). SREBP's are localized in the endoplasmic reticulum, but in the event that the cell needs to synthesize cholesterol, the NH2-terminal portion of these proteins is cleaved by two specific proteases, and then travels into the nucleus to function as transcriptional factor. The present review shows the details of the mechanism that the cell uses to regulate cholesterol biosynthesis by the SREBP's, and its potential metabolic implications.

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