Gamma-glutamyl carboxylase is an enzyme that catalyzes the posttranslational modification of vitamin K-dependent proteins. Many of these vitamin K-dependent proteins are involved in coagulation so the function of the encoded enzyme is essential for hemostasis.[2] Most gla domain-containing proteins depend on this carboxylation reaction for posttranslational modification.[3] In humans, the gamma-glutamyl carboxylase enzyme is most highly expressed in the liver.
Catalytic reaction
Gamma-glutamyl carboxylase oxidizes Vitamin K hydroquinone to Vitamin K 2,3 epoxide, while simultaneously adding CO2 to protein-bound glutamic acid (abbreviation = Glu) to form gamma-carboxyglutamic acid (also called gamma-carboxyglutamate, abbreviation = Gla). The carboxylation reaction will only proceed if the carboxylase enzyme is able to oxidize vitamin K hydroquinone to vitamin K epoxide at the same time; the carboxylation and epoxidation reactions are said to be coupled reactions.[4][5][6]
a [protein]-α-L-glutamate (Glu) + phylloquinol (KH 2) + CO 2 + oxygen →
a [protein] 4-carboxy-L-glutamate (Gla) + vitamin K 2,3-epoxide (KO) + H+ + H 2O
Clinical significance
Mutations in this gene are associated with vitamin K-dependent coagulation defect and PXE-like disorder with multiple coagulation factor deficiency.[2][7]
↑Brenner B, Tavori S, Zivelin A, Keller CB, Suttie JW, Tatarsky I, Seligsohn U (August 1990). "Hereditary deficiency of all vitamin K-dependent procoagulants and anticoagulants". Br. J. Haematol. 75 (4): 537–42. doi:10.1111/j.1365-2141.1990.tb07795.x. PMID2145029.
↑Silva PJ, Ramos MJ (2007). "Reaction mechanism of the vitamin K-dependent glutamate carboxylase: a computational study". J Phys Chem B. 111 (44): 12883–7. doi:10.1021/jp0738208. PMID17935315.
↑Vanakker OM, Martin L, Gheduzzi D, Leroy BP, Loeys BL, Guerci VI, Matthys D, Terry SF, Coucke PJ, Pasquali-Ronchetti I, De Paepe A (March 2007). "Pseudoxanthoma elasticum-like phenotype with cutis laxa and multiple coagulation factor deficiency represents a separate genetic entity". J. Invest. Dermatol. 127 (3): 581–7. doi:10.1038/sj.jid.5700610. PMID17110937.
Further reading
Bandyopadhyay PK (2008). "Vitamin K-dependent gamma-glutamylcarboxylation: an ancient posttranslational modification". Vitam. Horm. 78: 157–84. doi:10.1016/S0083-6729(07)00008-8. PMID18374194.