acyl-[acyl-carrier-protein] desaturase | |||||||||
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![]() Partially occupied Stearoyl Acyl Carrier Protein Desaturase from Ricinius Communis | |||||||||
Identifiers | |||||||||
EC no. | 1.14.19.2 | ||||||||
CAS no. | 37256-86-3 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
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In enzymology, an acyl-[acyl-carrier-protein] desaturase (EC 1.14.19.2) is an enzyme that catalyzes the chemical reaction
The systematic name of this enzyme class is acyl-[acyl-carrier-protein], hydrogen-donor:oxygen oxidoreductase. Other names in common use include stearyl acyl carrier protein desaturase, and stearyl-ACP desaturase. This enzyme participates in polyunsaturated fatty acid biosynthesis. It employs one cofactor, ferredoxin. [1]
The 3 substrates of this enzyme are stearoyl-(acyl-carrier-protein), reduced acceptor, and O2, whereas its 3 products are oleoyl-(acyl-carrier-protein), acceptor, and H2O. [2]
The precise mechanism of this class of enzymes is not known, however recent studies using the kinetic isotope effect suggest that the rate limiting step is the removal of a hydrogen from the carbon nearest the carboxylic acid group. The diiron cluster moves through to a peroxo intermediate which can then dehydrate the short-lived alcohol intermediate, liberating water. [3] There are a variety of specific enzymes within this class that attack using this mechanism, but do so at different points along the carbon chain of their respective fatty acids [3]
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with oxidation of a pair of donors resulting in the formation of H2O.
This family of enzymes is found only in the plastids of higher plant cells, unlike other desaturases such as acyl-lipid desaturases and acyl-CoA desaturases. [4] The regiospecific role of stearoyl-ACP desaturase is to initialise multiple desaturations by acyl-lipid desaturases. Oleic acid is formed from this reaction is transported to either the thylakoid or cytoplasm to complete desaturation. [5]
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes 1OQ4, 1OQ7, 1OQ9, 1OQB, and 1ZA0.
2XZ0 and 2XZ1 show the dramatic change in conformation of the enzyme when bound (2XZ1) and unbound (2XZ0). As a dimer, the fatty acid chain binds to a hydrophobic pocket at the interface of the two dimers,. [6] This central channel is mirrored by binding sites for the electron donors on either side.
The stabilisation of the diiron-oxo element required to catalyse the reaction has been of particular interest. Crystallographic studies [7] suggest that the iron groups are held in place by the desaturase using aspartate and glutamate. A structure of aspartate-X-X-histidine was found to be a common motif in several plant species. [8] This desaturase family can be further divided by the consensus motif used to hold the iron clusters in place. Of particular note are the "soluble" desaturases, which use carboxylic acid groups, whereas it is possible for some variants to use histidines instead. The histidine rich desaturases tend to be integral membrane proteins. [6]
Structural studies strongly suggest that the animal form of this enzyme (Stearoyl-acyl-carrier-protein desaturase) is evolutionarily divergent from the forms found in plants and fungi. [9] This is to be expected as the roles of the enzymes are different in both. For example, in insects, the desaturase is critical in the formation of ceramide, and for complex signalling molecules (pheremones), [3] while in fungi, the function of the enzyme, and concentration of unsaturated lipids is regulated in response to function of growth temperature by controlling membrane fluidity in cells. [10]
This enzyme class plays a critical role in the biosynthesis of unsaturated fatty acids in plants, and are very specific to their substrates. [3] A common theme in recent research has been to identify uncommon desaturases in various plants [6] [11] and isolate their genetic code. In particular, this can then be inserted into model cells (such as Escherichia coli) and up-regulated through metabolic engineering to skew the composition of oils produced by the model cells. [12]
This becomes a particularly lucrative endeavour if it becomes possible to successfully synthesise so-called Omega-3 fatty acids or other nutraceutical products from basic saturated fatty acids, and extract them from their hosts.
Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All genomes sequenced to date encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it (or a thioester) as a substrate. In humans, CoA biosynthesis requires cysteine, pantothenate (vitamin B5), and adenosine triphosphate (ATP).
Fatty acid desaturases are a family of enzymes that convert saturated fatty acids into unsaturated fatty acids and polyunsaturated fatty acids. For the common fatty acids of the C18 variety, desaturases convert stearic acid into oleic acid. Other desaturases convert oleic acid into linolenic acid, which is the precursor to alpha-linolenic acid, gamma-linolenic acid, and eicosatrienoic acid.
Cytochromes b5 are ubiquitous electron transport hemoproteins found in animals, plants, fungi and purple phototrophic bacteria. The microsomal and mitochondrial variants are membrane-bound, while bacterial and those from erythrocytes and other animal tissues are water-soluble. The family of cytochrome b5-like proteins includes hemoprotein domains covalently associated with other redox domains in flavocytochrome cytochrome b2, sulfite oxidase, plant and fungal nitrate reductases, and plant and fungal cytochrome b5/acyl lipid desaturase fusion proteins.
Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group. Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides.
In biochemistry, fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. This process takes place in the cytoplasm of the cell. Most of the acetyl-CoA which is converted into fatty acids is derived from carbohydrates via the glycolytic pathway. The glycolytic pathway also provides the glycerol with which three fatty acids can combine to form triglycerides, the final product of the lipogenic process. When only two fatty acids combine with glycerol and the third alcohol group is phosphorylated with a group such as phosphatidylcholine, a phospholipid is formed. Phospholipids form the bulk of the lipid bilayers that make up cell membranes and surrounds the organelles within the cells.
In molecular biology, Beta-ketoacyl-ACP synthase EC 2.3.1.41, is an enzyme involved in fatty acid synthesis. It typically uses malonyl-CoA as a carbon source to elongate ACP-bound acyl species, resulting in the formation of ACP-bound β-ketoacyl species such as acetoacetyl-ACP.
In enzymology, a cholesterol 25-hydroxylase (EC 1.14.99.38) is an enzyme that catalyzes the chemical reaction
In enzymology, a Delta12-fatty acid dehydrogenase (EC 1.14.99.33) is an enzyme that catalyzes the chemical reaction
In enzymology, a linoleoyl-CoA desaturase (also Delta 6 desaturase, EC 1.14.19.3) is an enzyme that converts between types of fatty acids, which are essential nutrients in the human body. The enzyme mainly catalyzes the chemical reaction
In enzymology, a plasmanylethanolamine desaturase (EC 1.14.99.19) is an enzyme that catalyzes the chemical reaction
Stearoyl-CoA desaturase (Δ-9-desaturase) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of monounsaturated fatty acids (MUFAs), specifically oleate and palmitoleate from stearoyl-CoA and palmitoyl-CoA. Oleate and palmitoleate are major components of membrane phospholipids, cholesterol esters and alkyl-diacylglycerol. In humans, the enzyme is encoded by the SCD gene.
Fatty acid desaturase 2 (FADS2) is encoded by the FADS2 gene, the associated enzyme is sometimes known as FADS2 as well. Its main associated enzyme is Delta 6 desaturase (D6D) however the human enzyme was shown to also catalyze some delta-8 and delta-4 desaturation reactions despite naming conventions.
In enzymology, a long-chain-fatty-acid—[acyl-carrier-protein] ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a [acyl-carrier-protein] S-acetyltransferase is an enzyme that catalyzes the reversible chemical reaction
In enzymology, a [acyl-carrier-protein] S-malonyltransferase is an enzyme that catalyzes the chemical reaction
Fatty acid desaturase 1 is an enzyme that in humans is encoded by the FADS1 gene.
Delta12-fatty-acid desaturase (EC 1.14.19.6, Delta12 fatty acid desaturase, Delta12(omega6)-desaturase, oleoyl-CoA Delta12 desaturase, Delta12 desaturase, Delta12-desaturase) is an enzyme with systematic name acyl-CoA,hydrogen donor:oxygen Delta12-oxidoreductase. This enzyme catalyses the following chemical reaction
3-hydroxydecanoyl-(acyl-carrier-protein) dehydratase (EC 4.2.1.60, D-3-hydroxydecanoyl-[acyl-carrier protein] dehydratase, 3-hydroxydecanoyl-acyl carrier protein dehydrase, 3-hydroxydecanoyl-acyl carrier protein dehydratase, β-hydroxydecanoyl thioester dehydrase, β-hydroxydecanoate dehydrase, beta-hydroxydecanoyl thiol ester dehydrase, FabA, β-hydroxyacyl-acyl carrier protein dehydratase, HDDase, β-hydroxyacyl-ACP dehydrase, (3R)-3-hydroxydecanoyl-[acyl-carrier-protein] hydro-lyase) is an enzyme with systematic name (3R)-3-hydroxydecanoyl-(acyl-carrier protein) hydro-lyase. This enzyme catalyses the following chemical reaction
Stearoyl-CoA is a coenzyme involved in the metabolism of fatty acids. Stearoyl-CoA is an 18-carbon long fatty acyl-CoA chain that participates in an unsaturation reaction. The reaction is catalyzed by the enzyme stearoyl-CoA desaturase, which is located in the endoplasmic reticulum. It forms a cis-double bond between the ninth and tenth carbons within the chain to form the product oleoyl-CoA.
Ketoacyl synthases (KSs) catalyze the condensation reaction of acyl-CoA or acyl-acyl ACP with malonyl-CoA to form 3-ketoacyl-CoA or with malonyl-ACP to form 3-ketoacyl-ACP. This reaction is a key step in the fatty acid synthesis cycle, as the resulting acyl chain is two carbon atoms longer than before. KSs exist as individual enzymes, as they do in type II fatty acid synthesis and type II polyketide synthesis, or as domains in large multidomain enzymes, such as type I fatty acid synthases (FASs) and polyketide synthases (PKSs). KSs are divided into five families: KS1, KS2, KS3, KS4, and KS5.