Summary: Fatty acid desaturase
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Fatty acid desaturase Edit Wikipedia article
|Fatty acid desaturase, type 1|
|Fatty acid desaturase, type 2|
- Delta - indicating that the double bond is created at a fixed position from the carboxyl end of a fatty acid chain. For example, Î”9 desaturase creates a double bond between the ninth and tenth carbon atom from the carboxyl end.
- Omega - indicating the double bond is created at a fixed position from the methyl end of a fatty acid chain. For instance, Ï‰3 desaturase creates a double bond between the third and fourth carbon atom from the methyl end. In other words, it creates an omega-3 fatty acid.
Maintain structure and function of membranes within cells of the organisms above. This is important when temperatures changes and the membrane is under distress. The enzyme creates the double bond C-Cs which allow the membrane to become more fluid and the temperature is decreased. When temperatures change, a phase transition occurs. In the case of a temperature decrease, the membrane gels and becomes solid which can result in cracks and the imbedded proteins cannot partake in conformational changes, therefore it is important to maintain membrane fluidity.
Role in human metabolism
Fatty acid desaturase appear in all organisms: for example, bacteria, fungus, plants, animals and humans. Four desaturases occur in humans: Î”9 desaturase, Î”6 desaturase, Î”5 desaturase, and Î”4 desaturase.
Î”9 desaturase, also known as stearoyl-CoA desaturase-1, is used to synthesize oleic acid, a monounsaturated, ubiquitous component of all cells in the human body. Î”9 desaturase produces oleic acid by desaturating stearic acid, a saturated fatty acid either synthesized in the body from palmitic acid or ingested directly.
Î”6 and Î”5 desaturases are required for the synthesis of highly unsaturated fatty acids such as eicosopentaenoic and docosahexaenoic acids (synthesized from Î±-linolenic acid); arachidonic acid and adrenic acid (synthesized from linoleic acid). This is a multi-stage process requiring successive actions by elongase and desaturase enzymes. The genes coding for Î”6 and Î”5 desaturase production have been located on human chromosome 11.
Vertebrates are unable to synthesize polyunsaturated fatty acids because they do not have the necessary fatty acid desaturases to "convert oleic acid (18:1n-9) into linoleic acid (18:2n-6) and Î±-linolenic acid (18:3n-3)". Linoleic acid and Î±-linolenic acid are essential for human health and development.
Î”-desaturases are represented by two distinct families which do not seem to be evolutionarily related.
Family 2 is composed of:
- Bacterial fatty acid desaturases.
- Plant stearoyl-acyl-carrier-protein desaturase (EC 220.127.116.11), an enzyme that catalyzes the introduction of a double bond at the delta-9 position of steraoyl-ACP to produce oleoyl-ACP. This enzyme is responsible for the conversion of saturated fatty acids to unsaturated fatty acids in the synthesis of vegetable oils.
- Cyanobacterial DesA, an enzyme that can introduce a second cis double bond at the delta-12 position of fatty acid bound to membrane glycerolipids. This enzyme is involved in chilling tolerance; the phase transition temperature of lipids of cellular membranes being dependent on the degree of unsaturation of fatty acids of the membrane lipids.
Acyl-CoA dehydrogenases are enzymes that catalyze formation of a double bond between C2 (Î±) and C3 (Î²) of the acyl-CoA thioester substrates. Flavin adenine dinucleotide (FAD) is a required co-factor.
- Los DA, Murata N (October 1998). "Structure and expression of fatty acid desaturases". Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism. 1394 (1): 3â€“15. doi:10.1016/S0005-2760(98)00091-5. PMIDÂ 9767077.
- Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). "The Fluidity of a Lipid Bilayer Depends on Its Composition". Molecular Biology of the Cell (4thÂ ed.). New York: Garland Science. p.Â 588. ISBNÂ 978-0-8153-3218-3.
- Nakamura MT, Nara TY (2004). "Structure, function, and dietary regulation of Î”6, Î”5, and Î”9 desaturases". Annual Review of Nutrition. 24 (1): 345â€“76. doi:10.1146/annurev.nutr.24.121803.063211. PMIDÂ 15189125.
- Hastings N, Agaba M, Tocher DR, Leaver MJ, Dick JR, Sargent JR, Teale AJ (December 2001). "A vertebrate fatty acid desaturase with Delta 5 and Delta 6 activities". Proceedings of the National Academy of Sciences of the United States of America. 98 (25): 14304â€“9. doi:10.1073/pnas.251516598. PMCÂ 64677. PMIDÂ 11724940.
- Kaestner KH, Ntambi JM, Kelly Jr TJ, Lane MD (September 1989). "Differentiation-induced gene expression in 3T3-L1 preadipocytes. A second differentially expressed gene encoding stearoyl-CoA desaturase" (PDF). The Journal of Biological Chemistry. 264 (25): 14755â€“61. doi:10.1016/S0021-9258(18)63763-9. PMIDÂ 2570068.
- Shanklin J, Somerville C (March 1991). "Stearoyl-acyl-carrier-protein desaturase from higher plants is structurally unrelated to the animal and fungal homologs". Proceedings of the National Academy of Sciences of the United States of America. 88 (6): 2510â€“4. Bibcode:1991PNAS...88.2510S. doi:10.1073/pnas.88.6.2510. PMCÂ 51262. PMIDÂ 2006187.
- Wada H, Gombos Z, Murata N (September 1990). "Enhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation". Nature. 347 (6289): 200â€“3. Bibcode:1990Natur.347..200W. doi:10.1038/347200a0. PMIDÂ 2118597. S2CIDÂ 4326551.
- Thorpe C, Kim JJ (June 1995). "Structure and mechanism of action of the acyl-CoA dehydrogenases". FASEB Journal. 9 (9): 718â€“25. doi:10.1096/fasebj.9.9.7601336. PMIDÂ 7601336. S2CIDÂ 42549744.
This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.
Fatty acid desaturase Provide feedback
Fatty acid desaturases are enzymes that catalyse the insertion of a double bond at the delta position of fatty acids. There seem to be two distinct families of fatty acid desaturases which do not seem to be evolutionary related: Family 1 composed of Stearoyl-CoA desaturases (SCD) [1,2] and Family 2 composed of Bacterial fatty acid desaturases, Plant stearoyl-acyl-carrier-protein desaturase  and Cyanobacterial DesA . Members of this entry are ER integral membrane proteins that share the same mushroom-shaped fold consisting of four transmembrane helices (TM1-TM4) which anchor them to the membrane, capped by a cytosolic domain containing a unique 9-10 histidine- coordinating di metal (di-iron) catalytic centre [5,6]. The structure of mouse stearoyl-CoA desaturase (SDC) revealed that TM2 and TM4 are longer than TM1 and TM3 and protrude into the cytosolic domain, providing three of the nine histidine residues that coordinate the two metal ions, while the other histidine residues are provided by the soluble domain in this enzyme .
Lindqvist Y, Huang W, Schneider G, Shanklin J; , EMBO J 1996;15:4081-4092.: Crystal structure of delta9 stearoyl-acyl carrier protein desaturase from castor seed and its relationship to other di-iron proteins. PUBMED:8861937 EPMC:8861937
Kaestner KH, Ntambi JM, Kelly TJ Jr, Lane MD;, J Biol Chem. 1989;264:14755-14761.: Differentiation-induced gene expression in 3T3-L1 preadipocytes. A second differentially expressed gene encoding stearoyl-CoA desaturase. PUBMED:2570068 EPMC:2570068
Shanklin J, Somerville C;, Proc Natl Acad Sci U S A. 1991;88:2510-2514.: Stearoyl-acyl-carrier-protein desaturase from higher plants is structurally unrelated to the animal and fungal homologs. PUBMED:2006187 EPMC:2006187
Wang H, Klein MG, Zou H, Lane W, Snell G, Levin I, Li K, Sang BC;, Nat Struct Mol Biol. 2015;22:581-585.: Crystal structure of human stearoyl-coenzyme A desaturase in complex with substrate. PUBMED:26098317 EPMC:26098317
Internal database links
|SCOOP:||7tm_1 DUF3474 Lipid_DES|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR005804
Fatty acid desaturases are enzymes that catalyse the insertion of a double bond at the delta position of fatty acids. There seem to be two distinct families of fatty acid desaturases which do not seem to be evolutionary related.
Family 1 is composed of:
Family 2 is composed of:
- Bacterial fatty acid desaturases.
- Plant stearoyl-acyl-carrier-protein desaturase ( EC ) [ PUBMED:2006187 ], this enzyme catalyzes the introduction of a double bond at the delta(9) position of steraoyl-ACP to produce oleoyl-ACP. This enzyme is responsible for the conversion of saturated fatty acids to unsaturated fatty acids in the synthesis of vegetable oils.
- Cyanobacterial DesA [ PUBMED:2118597 ], an enzyme that can introduce a second cis double bond at the delta(12) position of fatty acid bound to membranes glycerolipids. DesA is involved in chilling tolerance; the phase transition temperature of lipids of cellular membranes being dependent on the degree of unsaturation of fatty acids of the membrane lipids.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Biological process||lipid metabolic process (GO:0006629)|
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Families in this clan are integral membrane di-iron-containing enzymes that share the same fold consisting of four transmembrane helices (TM1-TM4) that anchor them to the endoplasmic reticulum (ER) membrane, capped by a cytosolic domain containing a unique 9-10 histidine-coordinating dimetal (di-iron) catalytic centre. This fold is found in fatty acid hydroxylases and fatty acid desaturases, which hydroxylate or desaturate lipid-based substrates in a NADH and oxygen-dependent reaction [1,2,3]. The structure of mouse stearoyl-CoA desaturase (SDC) revealed that TM2 and TM4 are longer than TM1 and TM3 and protrude into the cytosolic domain, providing three of the nine histidine residues that coordinate the two metal ions, while the other histidine residues are provided by the soluble domain in this enzyme .
The clan contains the following 3 members:FA_desaturase FA_hydroxylase Lipid_desat
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|Seed source:||Bateman A|
|Author:||Finn RD , Bateman A|
|Number in seed:||125|
|Number in full:||28403|
|Average length of the domain:||242.40 aa|
|Average identity of full alignment:||15 %|
|Average coverage of the sequence by the domain:||64.45 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||27|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the FA_desaturase domain has been found. There are 4 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.
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AlphaFold Structure Predictions
The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.