MCB - 64 - Fatty Acid Biosynthesis Flashcards | Quizlet

TesA involves in the biosynthesis of fatty acids in . The biosynthesis pathway is shown as below:

Fatty Acid Biosynthesis Flashcards ..

The branched-chain fatty acid synthesizing system uses as primers. This system is distinct from the branched-chain fatty acid synthetase that utilizes short-chain acyl-CoA esters as primers. α-Keto acid primers are derived from the and of , , and to form 2-methylpropanyl-CoA, 3-methylbutyryl-CoA, and 2-Methylbutyryl-CoA, respectively. 2-Methylpropanyl-CoA primers derived from valine are elongated to produce even-numbered iso-series fatty acids such as 14-methyl-pentadecanoic (isopalmitic) acid, and 3-methylbutyryl-CoA primers from leucine may be used to form odd-numbered iso-series fatty acids such as 13-methyl-tetradecanoic acid. 2-Methylbutyryl-CoA primers from isoleucine are elongated to form anteiso-series fatty acids containing an odd number of carbon atoms such as 12-Methyl tetradecanoic acid. Decarboxylation of the primer precursors occurs through the (BCKA) enzyme. Elongation of the fatty acid follows the same biosynthetic pathway in used to produce straight-chain fatty acids where malonyl-CoA is used as a chain extender. The major end products are 12–17 carbon branched-chain fatty acids and their composition tends to be uniform and characteristic for many bacterial species.

Straight-chain fatty acids occur in two types: saturated and unsaturated.

Committed Step In Fatty Acid Synthesis

Acetyl-CoA is formed into malonyl-CoA by , at which point malonyl-CoA is destined to feed into the fatty acid synthesis pathway. Acetyl-CoA carboxylase is the point of regulation in saturated straight-chain fatty acid synthesis, and is subject to both and . Regulation by phosphorylation occurs mostly in mammals, while allosteric regulation occurs in most organisms. Allosteric control occurs as feedback inhibition by palmitoyl-CoA and activation by citrate. When there are high levels of palmitoyl-CoA, the final product of saturated fatty acid synthesis, it allosterically inactivates acetyl-CoA carboxylase to prevent a build-up of fatty acids in cells. Citrate acts to activate acetyl-CoA carboxylase under high levels, because high levels indicate that there is enough acetyl-CoA to feed into the and produce energy.

In humans, fatty acids are formed from carbohydrates predominantly in the  and , as well as in the  during lactation.

Aerobic desaturation is the most widespread pathway for the synthesis of unsaturated fatty acids. It is utilized in all eukaryotes and some prokaryotes. This pathway utilizes to synthesize unsaturated fatty acids from full-length saturated fatty acid substrates. All desaturases require oxygen and ultimately consume NADH even though desaturation is an oxidative process. Desaturases are specific for the double bond they induce in the substrate. In , the desaturase, Δ5-Des, is specific for inducing a cis-double bond at the Δ5 position. contains one desaturase, Ole1p, which induces the cis-double bond at Δ9.

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Amino Acid Biosynthesis - eLS: Essential for Life Science

In general, both anaerobic and aerobic unsaturated fatty acid synthesis will not occur within the same system, however and ABE-1 are exceptions. While undergoes primarily anaerobic desaturation, it also undergoes two aerobic pathways. One pathway utilizes a Δ9-desaturase (DesA) that catalyzes a double bond formation in membrane lipids. Another pathway uses two proteins, DesC and DesB, together to act as a Δ9-desaturase, which inserts a double bond into a saturated fatty acid-CoA molecule. This second pathway is regulated by repressor protein DesT. DesT is also a repressor of expression for anaerobic desaturation when in presence of exogenous unsaturated fatty acids. This functions to coordinate the expression of the two pathways within the organism.

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High plasma levels of in the blood plasma (e.g. after meals) cause the dephosphorylation of acetyl-CoA carboxylase, thus promoting the formation of malonyl-CoA from acetyl-CoA, and consequently the conversion of carbohydrates into fatty acids, while and (released into the blood during starvation and exercise) cause the phosphorylation of this enzyme, inhibiting in favor of fatty acid oxidation via .

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Branched-chain fatty acids are usually saturated and are found in two distinct families: the iso-series and anteiso-series. It has been found that contain unique branch-chain fatty acid synthesis mechanisms, including that which forms tuberculosteric acid.

Fatty acid synthesis is the creation of fatty acids from acetyl-CoA, via malonyl-CoA, through the action of enzymes called fatty acid synthases

The branched-chain fatty acid synthesizing system uses as primers. This system is distinct from the branched-chain fatty acid synthetase that utilizes short-chain acyl-CoA esters as primers. α-Keto acid primers are derived from the and of , , and to form 2-methylpropanyl-CoA, 3-methylbutyryl-CoA, and 2-Methylbutyryl-CoA, respectively. 2-Methylpropanyl-CoA primers derived from valine are elongated to produce even-numbered iso-series fatty acids such as 14-methyl-pentadecanoic (isopalmitic) acid, and 3-methylbutyryl-CoA primers from leucine may be used to form odd-numbered iso-series fatty acids such as 13-methyl-tetradecanoic acid. 2-Methylbutyryl-CoA primers from isoleucine are elongated to form anteiso-series fatty acids containing an odd number of carbon atoms such as 12-Methyl tetradecanoic acid. Decarboxylation of the primer precursors occurs through the (BCKA) enzyme. Elongation of the fatty acid follows the same biosynthetic pathway in used to produce straight-chain fatty acids where malonyl-CoA is used as a chain extender. The major end products are 12–17 carbon branched-chain fatty acids and their composition tends to be uniform and characteristic for many bacterial species.