The lipid portion of the endotoxin, lipid A, is chemically distinct from allother lipids in biological membranes and consists of characteristic 3-hydroxyfatty acids, primarily with carbon chain lengths from 10 to 18, attached tohydroxyl and amino groups of a disaccharide backbone. It has been proposedthat 3-hydroxy fatty acid quantification may be employed as biomarkers ofendotoxins and Gram-negative bacterial community in atmospheric aerosols ().
Transfer of acyl moiety to ACP (acyl carrier protein): The basic building blocks of FA synthesis are acetyl and malonyl groups.
They are first transferred to ACP by MAT (malonyl-CoA-acetyl-CoA-ACP transacylase) instead of being transferred directly from CoA to growing FA chain.
Novel insights into seed fatty acid synthesis and modification pathways from genetic diversity and quantitative trait Loci analysis of the brassica C genome.
Mammalian FAS (Fatty Acyl Synthases): Six functional domains FA’s additional elongation: Introduction of a single cis double bond: Biosynthesis of a monounsaturated FA: Additional elongation step
Palmitoleoyl–ACP is the substrate Mammals cannot synthesize most polyunsaturated fatty acids Mammals require polyunsaturated fatty acids but must require them in diet
Essential Fatty acids
But mammals can introduce double bond at C8,C9 and the carboxyl group Synthesis of arachidonic acid Substrate: Linoleic Acid
Precursor for prostaglandin In eukaryotes
Addition of double bond (in C16-C18)
Catalyzed by stearoyl–CoA desaturase
NADH and Oxygen are also required!
CH -(CH ) -CO-SCoA CH -(CH ) CH=CH(CH ) CO-SCoA Unsaturation Reaction in the middle of an aliphatic chain 3 2 16 3 2 7 2 7 Unsaturation Reaction in the middle of an aliphatic chain Notice that 2H2O are formed in the result:
2 electrons come from NADH
2 electrons come from substrate
(Formation of a double bond) Chain Elongation can also follow the unsaturation reaction:
C16 and C16 fatty acids can be elongated to yield C22 and C24 fatty acids
Often in sphingolipids.
References: Q&A Introduction Reeson Wang
Gavin Chan β FATTY ACID SYNTHESIS Synthesis Degration -SH group of ACPs (acyl carrier proteins) Coenzyme NADP+/NADPH NAD+/NADH Cytosol Mitochondria -SH group of CoA Occur at Intermediates linked to Various uses in the human body that range from energy production to controlling hormones
Biochemistry, 4th edition, Reginald H.
COO - Palmitic acid Design strategy for FA synthesis: FA chains are constructed by the addition of malonyl-CoA, activated form of acetyl-CoA.
The addition of malonyl-CoA is driven by decarboxylation of it.
The elongation reactions are repeated until reaching 16 carbons (palmitic acid) in length.
Other enzymes then add double bonds and additional carbon units to the chain.
These ester-bound fatty acids are unsaturated, the monoene (n-9) having a C30, C32 or C34 carbon chain and the diene (n-18 and n-19) having a C30 and C32 carbon chain.
Purification and properties of the Streptomyces peucetius DpsC beta-ketoacyl:acyl carrier protein synthase III that specifies the propionate-starter unit for type II polyketide biosynthesis.
At higher concentrations (1 to 20 mM), 4-HNEinhibits DNA and protein synthesis and activates phospholipase A2 confirmingsimilar observations in tissue in response to oxidative stress.
Thus, hydroperoxy aldehydes may undergo cleavage togive shorter chain aldehydes, sometimes with other chemical groups.
Among all these substances, malonaldehyde (MDA) isthe object of a great interest despite its complex and yet not completely cleared origin.
Various precursors of MDA have been proposed but the most probable and the mostbiochemically important seem to be the monocyclic peroxides formed from fatty acids with 3or more double bonds.
Thus, thromboxane synthetase generates MDA, with thromboxane A2, from prostaglandin endoperoxides during human platelet activation (Hecker M et al., J Biol Chem 1989, 264, 141).
As 4-HNE, MDA is able to form adducts with free amino acids and many more with proteins.
Studies areneeded to determine the diet and lifestyle patterns that enhance conversion to the long-chain omega-3 fatty acids.
Efficiency of Conversion of ALA.
In general, oxylipins are bioactive metabolites involved in regulating developmental processes and in environmental and pathological responses.
Very-long-chain fatty acids (C28C34) containing a hydroxy group at the n-18 position have been identified in the microalgae from the genus
Castor oil is also used to make emulsifier after transesterification of fatty acids from the glycerol to the hydroxyl group in ricinoleic acid and ethoxylation to give castor oil polyethylene glycol ().
The production of conjugated linoleic acid by dehydration and isomerization of ricinoleic acid has been described ().
Castor oil can be reacted with sulfuric acid to make Turkey-Red Oil, the first synthetic detergent or surfactant after ordinary soap, a predecessor to sodium lauryl sulfate.
Animal fatty acid synthases are large polypeptides containing seven functional domains that are active only in the dimeric form. Inactivity of the monomeric form has long been attributed to the obligatory participation of domains from both subunits in catalysis of substrate loading and condensation reactions. However, we have engineered a fatty acid synthase containing one wild-type subunit and one subunit compromised by mutations in all seven functional domains that is active in fatty acid synthesis. This finding indicates that a single subunit, in the context of a dimer, is able to catalyze the entire biosynthetic pathway and suggests that, in the natural complex, each of the two subunits forms a scaffold that optimizes the conformation of the companion subunit.