VKORC1
VKORC1 | |||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||||||||||
Aliases | VKORC1, EDTP308, IMAGE3455200, MST134, MST576, VKCFD2, VKOR, vitamin K epoxide reductase complex subunit 1 | ||||||||||||||||
External IDs | MGI: 106442 HomoloGene: 11416 GeneCards: VKORC1 | ||||||||||||||||
Targeted by Drug | |||||||||||||||||
alitretinoin, dicumarol, phenindione, Phenprocoumon, warfarin[1] | |||||||||||||||||
| |||||||||||||||||
RNA expression pattern | |||||||||||||||||
More reference expression data | |||||||||||||||||
Orthologs | |||||||||||||||||
Species | Human | Mouse | |||||||||||||||
Entrez | |||||||||||||||||
Ensembl | |||||||||||||||||
UniProt | |||||||||||||||||
RefSeq (mRNA) | |||||||||||||||||
RefSeq (protein) | |||||||||||||||||
Location (UCSC) | Chr 16: 31.09 – 31.1 Mb | Chr 7: 127.89 – 127.9 Mb | |||||||||||||||
PubMed search | [2] | [3] | |||||||||||||||
Wikidata |
View/Edit Human | View/Edit Mouse |
The human gene VKORC1 encodes for the enzyme, Vitamin K epOxide Reductase Complex (VKORC) subunit 1.[4] This enzymatic protein complex is responsible for reducing vitamin K 2,3-epoxide to its active form, which is important for effective clotting. In humans, mutations in this gene can be associated with deficiencies in vitamin-K-dependent clotting factors.
Function
Vitamin K is a family of molecules that are essential to blood clotting. Vitamin K 2,3-epoxide is activated by reduction via the VKORC enzyme. The activated form is then responsible for the carboxylation of glutamic acid residues in some blood-clotting proteins. These proteins are known as vitamin-K-dependent clotting factors.[4][5]
Gene
The human gene is located on chromosome 16. Two pseudogenes have been identified on chromosome 1 and the X chromosome.
Clinical relevance
In humans, mutations in this gene are associated with deficiencies in vitamin-K-dependent clotting factors. Fatal bleeding (internal) and hemorrhage can result from a decreased ability to form clots.
The product of the VKORC1 gene encodes a subunit of the enzyme that is responsible for reducing vitamin K 2,3-epoxide to the activated form, a reduction reaction. A genetic polymorphism on the VKORC1 gene results in a patient having less available VKORC enzyme to complete this reaction.
Specifically, in the VKORC1 1639 (or 3673) single-nucleotide polymorphism, the common ("wild-type") G allele is replaced by the A allele. People with an A allele (or the "A haplotype") produce less VKORC1 than do those with the G allele (or the "non-A haplotype"). The prevalence of these variants also varies by race, with 37% of Caucasians and 14% of Africans carrying the A allele. The end result is a decreased amount of clotting factors and therefore, a decreased ability to clot.
Warfarin is an anticoagulant that opposes the procoagulant effect of vitamin K by inhibiting the VKORC enzyme. If these patients are prescribed warfarin for another medical purpose, they will require lower doses than usual because the patient is already deficient in VKORC. They may experience severe bleeding and bruising. Lower warfarin doses are needed to inhibit VKORC1 and to produce an anticoagulant effect in carriers of the A allele. Genetic testing can reveal the presence of the genetic mutation and FDA recommends lower starting doses of warfarin in these patients.
Two alternatively spliced transcripts encoding different isoforms have also been described. These isoforms result in warfarin resistance (requiring higher doses) in humans and rats, because the amount and effectiveness of the VKORC enzyme has not changed, but the ability of warfarin to exert it's effect (antagonize the enzyme) has changed. These isoform mutations are rare except in Ethiopian and certain Jewish populations.
References
- ↑ "Drugs that physically interact with Vitamin K epoxide reductase complex subunit 1 view/edit references on wikidata".
- ↑ "Human PubMed Reference:".
- ↑ "Mouse PubMed Reference:".
- 1 2 "Entrez Gene: VKORC1 vitamin K epoxide reductase complex, subunit 1".
- ↑ Garcia AA, Reitsma PH (2008). "VKORC1 and the vitamin K cycle". Vitamins and Hormones. 78: 23–33. doi:10.1016/S0083-6729(07)00002-7. PMID 18374188.
Further reading
- Oldenburg J, Bevans CG, Müller CR, Watzka M (2006). "Vitamin K epoxide reductase complex subunit 1 (VKORC1): the key protein of the vitamin K cycle". Antioxidants & Redox Signaling. 8 (3-4): 347–53. doi:10.1089/ars.2006.8.347. PMID 16677080.
- Zhang J, Chen Z, Chen C (2016). "Impact of CYP2C9, VKORC1 and CYP4F2 genetic polymorphisms on maintenance warfarin dosage in Han-Chinese patients: A systematic review and meta-analysis". Meta Gene. 9: 197–209. doi:10.1016/j.mgene.2016.07.002. PMC 5006145. PMID 27617219.
- Takeuchi M, Kobayashi T, Brandão LR, Ito S (2016). "Effect of CYP2C9, VKORC1, and CYP4F2 polymorphisms on warfarin maintenance dose in children aged less than 18 years: a protocol for systematic review and meta-analysis". Systematic Reviews. 5 (1): 105. doi:10.1186/s13643-016-0280-y. PMC 4917995. PMID 27334984.
- Zhang J, Tian L, Zhang Y, Shen J (2015). "The influence of VKORC1 gene polymorphism on warfarin maintenance dosage in pediatric patients: A systematic review and meta-analysis". Thrombosis Research. 136 (5): 955–61. doi:10.1016/j.thromres.2015.09.018. PMID 26433837.
- Czogalla KJ, Watzka M, Oldenburg J (2015). "Structural Modeling Insights into Human VKORC1 Phenotypes". Nutrients. 7 (8): 6837–51. doi:10.3390/nu7085313. PMC 4555152. PMID 26287237.
- Shaw K, Amstutz U, Kim RB, Lesko LJ, Turgeon J, Michaud V, Hwang S, Ito S, Ross C, Carleton BC (2015). "Clinical Practice Recommendations on Genetic Testing of CYP2C9 and VKORC1 Variants in Warfarin Therapy". Therapeutic Drug Monitoring. 37 (4): 428–36. doi:10.1097/FTD.0000000000000192. PMID 26186657.
- Gaikwad T, Ghosh K, Shetty S (2014). "VKORC1 and CYP2C9 genotype distribution in Asian countries". Thrombosis Research. 134 (3): 537–44. doi:10.1016/j.thromres.2014.05.028. PMID 24908449.
- Yang J, Chen Y, Li X, Wei X, Chen X, Zhang L, Zhang Y, Xu Q, Wang H, Li Y, Lu C, Chen W, Zeng C, Yin T (2013). "Influence of CYP2C9 and VKORC1 genotypes on the risk of hemorrhagic complications in warfarin-treated patients: a systematic review and meta-analysis". International Journal of Cardiology. 168 (4): 4234–43. doi:10.1016/j.ijcard.2013.07.151. PMID 23932037.
- Fung E, Patsopoulos NA, Belknap SM, O'Rourke DJ, Robb JF, Anderson JL, Shworak NW, Moore JH (2012). "Effect of genetic variants, especially CYP2C9 and VKORC1, on the pharmacology of warfarin". Seminars in Thrombosis and Hemostasis. 38 (8): 893–904. doi:10.1055/s-0032-1328891. PMC 4134937. PMID 23041981.
- Jorgensen AL, FitzGerald RJ, Oyee J, Pirmohamed M, Williamson PR (2012). "Influence of CYP2C9 and VKORC1 on patient response to warfarin: a systematic review and meta-analysis". Plos One. 7 (8): e44064. doi:10.1371/journal.pone.0044064. PMC 3430615. PMID 22952875.
- Johnson JA, Gong L, Whirl-Carrillo M, Gage BF, Scott SA, Stein CM, Anderson JL, Kimmel SE, Lee MT, Pirmohamed M, Wadelius M, Klein TE, Altman RB (2011). "Clinical Pharmacogenetics Implementation Consortium Guidelines for CYP2C9 and VKORC1 genotypes and warfarin dosing". Clinical Pharmacology and Therapeutics. 90 (4): 625–9. doi:10.1038/clpt.2011.185. PMC 3187550. PMID 21900891.