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Acyl-CoA thioesterase 13 is a protein that in humans is encoded by the ACOT13 gene.[5] This gene encodes a member of the thioesterase superfamily. In humans, the protein co-localizes with microtubules and is essential for sustained cell proliferation.[5]
Structure
The orthologous mouse protein forms a homotetramer and is associated with mitochondria. The mouse protein functions as a medium- and long-chain acyl-CoA thioesterase. Multiple transcript variants encoding different isoforms have been found for this gene.[5]
Function
The protein encoded by the ACOT13 gene is part of a family of Acyl-CoAthioesterases, which catalyze the hydrolysis of various Coenzyme A esters of various molecules to the free acid plus CoA. These enzymes have also been referred to in the literature as acyl-CoA hydrolases, acyl-CoA thioester hydrolases, and palmitoyl-CoA hydrolases. The reaction carried out by these enzymes is as follows:
CoA ester + H2O → free acid + coenzyme A
These enzymes use the same substrates as long-chain acyl-CoA synthetases, but have a unique purpose in that they generate the free acid and CoA, as opposed to long-chain acyl-CoA synthetases, which ligate fatty acids to CoA, to produce the CoA ester.[6] The role of the ACOT- family of enzymes is not well understood; however, it has been suggested that they play a crucial role in regulating the intracellular levels of CoA esters, Coenzyme A, and free fatty acids. Recent studies have shown that Acyl-CoA esters have many more functions than simply an energy source. These functions include allosteric regulation of enzymes such as acetyl-CoA carboxylase,[7]hexokinase IV,[8] and the citrate condensing enzyme. Long-chain acyl-CoAs also regulate opening of ATP-sensitive potassium channels and activation of Calcium ATPases, thereby regulating insulin secretion.[9] A number of other cellular events are also mediated via acyl-CoAs, for example signal transduction through protein kinase C, inhibition of retinoic acid-induced apoptosis, and involvement in budding and fusion of the endomembrane system.[10][11][12] Acyl-CoAs also mediate protein targeting to various membranes and regulation of G Protein α subunits, because they are substrates for protein acylation.[13] In the mitochondria, acyl-CoA esters are involved in the acylation of mitochondrial NAD+ dependent dehydrogenases; because these enzymes are responsible for amino acid catabolism, this acylation renders the whole process inactive. This mechanism may provide metabolic crosstalk and act to regulate the NADH/NAD+ ratio in order to maintain optimal mitochondrial beta oxidation of fatty acids.[14] The role of CoA esters in lipid metabolism and numerous other intracellular processes are well defined, and thus it is hypothesized that ACOT- enzymes play a role in modulating the processes these metabolites are involved in.[15]
^Ogiwara H, Tanabe T, Nikawa J, Numa S (Aug 1978). "Inhibition of rat-liver acetyl-coenzyme-A carboxylase by palmitoyl-coenzyme A. Formation of equimolar enzyme-inhibitor complex". European Journal of Biochemistry. 89 (1): 33–41. doi:10.1111/j.1432-1033.1978.tb20893.x. PMID29756.
^Srere PA (Dec 1965). "Palmityl-coenzyme A inhibition of the citrate-condensing enzyme". Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism. 106 (3): 445–55. doi:10.1016/0005-2760(65)90061-5. PMID5881327.
^Hunt MC, Alexson SE (Mar 2002). "The role Acyl-CoA thioesterases play in mediating intracellular lipid metabolism". Progress in Lipid Research. 41 (2): 99–130. doi:10.1016/s0163-7827(01)00017-0. PMID11755680.
Venkatesh SK, Siddaiah A, Padakannaya P, Ramachandra NB (Oct 2013). "Lack of association between genetic polymorphisms in ROBO1, MRPL19/C2ORF3 and THEM2 with developmental dyslexia". Gene. 529 (2): 215–9. doi:10.1016/j.gene.2013.08.017. PMID23954868.
Cheng Z, Bao S, Shan X, Xu H, Gong W (Dec 2006). "Human thioesterase superfamily member 2 (hTHEM2) is co-localized with beta-tubulin onto the microtubule". Biochemical and Biophysical Research Communications. 350 (4): 850–3. doi:10.1016/j.bbrc.2006.09.105. PMID17045243.
Walker LC, Waddell N, Ten Haaf A, Grimmond S, Spurdle AB (Nov 2008). "Use of expression data and the CGEMS genome-wide breast cancer association study to identify genes that may modify risk in BRCA1/2 mutation carriers". Breast Cancer Research and Treatment. 112 (2): 229–36. doi:10.1007/s10549-007-9848-5. PMID18095154. S2CID795870.
Cheng Z, Song F, Shan X, Wei Z, Wang Y, Dunaway-Mariano D, Gong W (Oct 2006). "Crystal structure of human thioesterase superfamily member 2". Biochemical and Biophysical Research Communications. 349 (1): 172–7. doi:10.1016/j.bbrc.2006.08.025. PMID16934754.
