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Abstract
Vitamin K-dependent carboxylation, an essential posttranslational modification catalyzed by gamma-glutamyl carboxylase, is required for the biological functions of proteins that control blood coagulation, vascular calcification, bone metabolism, and other important physiological processes. Concomitant with carboxylation, reduced vitamin K (KH2) is oxidized to vitamin K epoxide (KO). KO must be recycled back to KH2 by the enzymes vitamin K epoxide reductase and vitamin K reductase in a pathway known as the vitamin K cycle. Our current knowledge about the enzymes of the vitamin K cycle is mainly based on in vitro studies of each individual enzymes under artificial conditions, which are of limited usefulness in understanding how the complex carboxylation process is carried out in the physiological environment. In this chapter, we review the current in vitro activity assays for vitamin K cycle enzymes. We describe the rationale, establishment, and application of cell-based assays for the functional study of these enzymes in the native cellular milieu. In these cell-based assays, different vitamin K-dependent proteins were designed and stably expressed in mammalian cells as reporter proteins to accommodate the readily used enzyme-linked immunosorbent assay for carboxylation efficiency evaluation. Additionally, recently emerged genome-editing techniques TALENs and CRISPR-Cas9 were used to knock out the endogenous enzymes in the reporter cell lines to eliminate the background. These cell-based assays are easy to scale up for high-throughput screening of inhibitors of vitamin K cycle enzymes and have been successfully used to clarify the genotypes and their clinical phenotypes of enzymes of the vitamin K cycle.
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Affiliation(s)
- J-K Tie
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
| | - D W Stafford
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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Rishavy MA, Hallgren KW, Berkner KL. The vitamin K-dependent carboxylase generates γ-carboxylated glutamates by using CO2 to facilitate glutamate deprotonation in a concerted mechanism that drives catalysis. J Biol Chem 2011; 286:44821-32. [PMID: 21896484 DOI: 10.1074/jbc.m111.249177] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The γ-glutamyl carboxylase converts Glu to carboxylated Glu (Gla) to activate a large number of vitamin K-dependent proteins with diverse functions, and this broad physiological impact makes it critical to understand the mechanism of carboxylation. Gla formation is thought to occur in two independent steps (i.e. Glu deprotonation to form a carbanion that then reacts with CO(2)), based on previous studies showing unresponsiveness of Glu deprotonation to CO(2). However, our recent studies on the kinetic properties of a variant enzyme (H160A) showing impaired Glu deprotonation prompted a reevaluation of this model. Glu deprotonation monitored by tritium release from the glutamyl γ-carbon was dependent upon CO(2), and a proportional increase in both tritium release and Gla formation occurred over a range of CO(2) concentrations. This discrepancy with the earlier studies using microsomes is probably due to the known accessibility of microsomal carboxylase to water, which reprotonates the carbanion. In contrast, tritium incorporation experiments with purified carboxylase showed very little carbanion reprotonation and consequently revealed the dependence of Glu deprotonation on CO(2). Cyanide stimulated Glu deprotonation and carbanion reprotonation to the same extent in wild type enzyme but not in the H160A variant. Glu deprotonation that depends upon CO(2) but that also occurs when water or cyanide are present strongly suggests a concerted mechanism facilitated by His-160 in which an electrophile accepts the negative charge on the developing carbanion. This revised mechanism provides important insight into how the carboxylase catalyzes the reaction by avoiding the formation of a high energy discrete carbanion.
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Affiliation(s)
- Mark A Rishavy
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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BORY SONIA, DUBOIS JOËLLE, GAUDRY MICHEL, MARQUET ANDRÉE. Vitamin-K-dependent carboxylation. ACTA ACUST UNITED AC 2009. [DOI: 10.1111/j.1399-3011.1984.tb03151.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Rishavy MA, Berkner KL. Insight into the coupling mechanism of the vitamin K-dependent carboxylase: mutation of histidine 160 disrupts glutamic acid carbanion formation and efficient coupling of vitamin K epoxidation to glutamic acid carboxylation. Biochemistry 2008; 47:9836-46. [PMID: 18717596 DOI: 10.1021/bi800296r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vitamin K-dependent (VKD) proteins become activated by the VKD carboxylase, which converts Glu's to carboxylated Glu's (Gla's) in their Gla domains. The carboxylase uses vitamin K epoxidation to drive Glu carboxylation, and the two half-reactions are coupled in 1:1 stoichiometry by an unknown mechanism. We now report the first identification of a residue, His160, required for coupling. A H160A mutant showed wild-type levels of epoxidation but substantially less carboxylation. Monitoring proton abstraction using a peptide with Glu tritiated at the gamma-carbon position revealed that poor coupling was due to impaired carbanion formation. H160A showed a 10-fold lower ratio of tritium release to vitamin K epoxidation than wild-type enzyme (i.e., 0.12 versus 1.14, respectively), which could fully account for the fold decrease in coupling efficiency. The Ala substitution in His160 did not affect the K m for vitamin K and caused only a 2-fold increase in the K m for Glu and 2-fold decrease in the activation of vitamin K epoxidation by Glu. The H160A K m for CO 2 was 5-fold higher than the wild-type enzyme. However, the k cat for H160A carboxylation was 8-9-fold lower than the wild-type enzyme with all three substrates (i.e., Glu, CO 2, and vitamin K), suggesting a catalytic role for His160 in carbanion formation. We propose that His160 facilitates the formation of the transition state for carbanion formation. His160 is highly conserved in metazoan VKD carboxylases but not in some bacterial orthologues (acquired by horizontal gene transfer), which has implications for how bacteria have adapted the carboxylase for novel functions.
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Affiliation(s)
- Mark A Rishavy
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA
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Black RS, Adams GM, Jorgenson JW, Hiskey RG. Counting Integral Numbers of γ-Carboxyglutamic Acids Per Peptide Chain Using Capillary Electrophoresis. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079708005560] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Roderick S. Black
- a Department of Chemistry , University of North Carolina at Chapel Hill , CB #3290, Venable Hall, Chapel Hill, North Carolina, 27599
| | - George M. Adams
- a Department of Chemistry , University of North Carolina at Chapel Hill , CB #3290, Venable Hall, Chapel Hill, North Carolina, 27599
| | - James W. Jorgenson
- a Department of Chemistry , University of North Carolina at Chapel Hill , CB #3290, Venable Hall, Chapel Hill, North Carolina, 27599
| | - Richard G. Hiskey
- a Department of Chemistry , University of North Carolina at Chapel Hill , CB #3290, Venable Hall, Chapel Hill, North Carolina, 27599
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Benton ME, Price PA, Suttie JW. Multi-site-specificity of the vitamin K-dependent carboxylase: in vitro carboxylation of des-gamma-carboxylated bone Gla protein and Des-gamma-carboxylated pro bone Gla protein. Biochemistry 1995; 34:9541-51. [PMID: 7626624 DOI: 10.1021/bi00029a031] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The vitamin K-dependent carboxylase processes multiple glutamic acid residues to gamma-carboxyglutamic acid (Gla) residues in a limited number of proteins. The targeted proteins are synthesized with an amino-terminal propeptide which has been shown to play an important role in gamma-carboxylation. The specificity of the enzyme for each potential Gla site, the direction of carboxylation, and the influence of a bound propeptide on these events are not understood. Des-gamma-carboxy forms of bone Gla protein (BGP), which contain potential Gla residues at positions 17, 21, and 24, were employed as model substrates to determine the multi-site-specificity of the enzyme. Recombinant bovine des-gamma-carboxylated proBGP (rdproBGP) and heat-decarboxylated BGP (dBGP), lacking a propeptide, were used as substrates for a bovine liver carboxylase, and the in vitro reaction products were analyzed for the formation of 14CO2 Gla. The di-Gla species was found to be the predominant product of in vitro carboxylation of both rdproBGP and dBGP at less than saturating concentrations of each substrate. Carboxylation of both substrates occurred preferentially at the more C-terminal potential Gla sites, residues 21 and 24. A similar pattern of carboxylation was observed with a rat bone cell carboxylase, suggesting no species or tissue variation in the enzyme specificity. Some tricarboxylated product accumulated during carboxylation of rdproBGP but not dBGP, suggesting that the covalently bound propeptide directs more complete carboxylation of the Gla domain. In addition, monocarboxylated rdproBGP was found to accumulate in the absence but not in the presence of a free noncovalently attached propeptide, indicating that free propeptide affects more efficient carboxylation of rdproBGP.
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Affiliation(s)
- M E Benton
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706-1569, USA
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Acher F, Azerad R. Synthesis of diastereoisomeric peptides incorporating cycloglutamic acids. Substrate specificity of vitamin K-dependent carboxylation. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1991; 37:210-9. [PMID: 1678382 DOI: 10.1111/j.1399-3011.1991.tb00272.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Tripeptides Boc-X-Glu-Val where X is alpha-methyl glutamic acid or various cyclic analogues of glutamic acid, such as 1-amino-1,3-dicarboxycyclohexane (cis or trans-CHGA) or -cyclopentane (cis or trans-CPGA) have been synthesized. Methods for the selective protection, activation, and coupling of such unnatural amino acids are described. The peptides, which are potential competitive inhibitors of the vitamin K-dependent carboxylation, have been preliminarily tested with the rat liver microsomal carboxylase and found to be effective substrates of the carboxylation reaction.
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Affiliation(s)
- F Acher
- Laboratory of Pharmacological and Toxicological Chemistry and Biochemistry, URA 400 CNRS, University René Descartes, Paris, France
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Furie B, Furie BC. Molecular basis of gamma-carboxylation. Role of the propeptide in the vitamin K-dependent proteins. Ann N Y Acad Sci 1991; 614:1-10. [PMID: 2024877 DOI: 10.1111/j.1749-6632.1991.tb43687.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- B Furie
- Center for Hemostasis and Thrombosis Research, New England Medical Center, Boston, Massachusetts
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Vidal-Cros A, Gaudry M, Marquet A. Vitamin K-dependent carboxylation. Mechanistic studies with 3-fluoroglutamate-containing substrates. Biochem J 1990; 266:749-55. [PMID: 2327963 PMCID: PMC1131203 DOI: 10.1042/bj2660749] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The tripeptides t-butyloxycarbonyl-Xaa-Glu-[3H]Val, where Xaa is either (2R,3S)- or (2R,3R)-3-fluoroglutamate (respectively the erythro and the threo isomer), were synthesized and their behaviour during vitamin K-dependent carboxylation was studied. Neither peptide was carboxylated. The erythro compound gave rise to an HF-elimination product representing 1% of the starting material. This HF elimination did not occur during incubation of the threo compound. The formation of the dehydropeptide, probably by elimination of an F- anion from an intermediate carbanion, favours the ionic pathway for vitamin K-dependent carboxylation.
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Affiliation(s)
- A Vidal-Cros
- Laboratoire de Chimie Organique Biologique, C.N.R.S. U.A. 493, Université Paris, France
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Ulrich MM, Furie B, Jacobs MR, Vermeer C, Furie BC. Vitamin K-dependent carboxylation. A synthetic peptide based upon the gamma-carboxylation recognition site sequence of the prothrombin propeptide is an active substrate for the carboxylase in vitro. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)81574-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Guibé E, Decottignies-Le Maréchal P, Le Maréchal P, Azerad R. Vitamin K-dependent carboxylation: inhibition by a peptide containing 4-methylene glutamic acid. FEBS Lett 1984; 177:265-8. [PMID: 6500053 DOI: 10.1016/0014-5793(84)81296-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The peptide Boc-4-methylene Glu-Glu-Val has been synthesized and shown to be a strong inhibitor of the vitamin K-dependent carboxylation catalyzed by a detergent solubilized rat liver microsome preparation. The inhibition is apparently competitive with respect to the substrate peptide and non-competitive with respect to HCO3-.
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McTigue JJ, Dhaon MK, Rich DH, Suttie JW. Vitamin K-dependent carboxylase. Carboxylation of aspartyl residues to beta-carboxyaspartyl residues in synthetic substrates. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43041-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Decottignies-Le Maréchal P, Le Maréchal P, Azerad R. Nature of products formed in the vitamin K-dependent carboxylation of synthetic peptides. Biochem Biophys Res Commun 1984; 119:836-40. [PMID: 6712674 DOI: 10.1016/0006-291x(84)90849-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Vitamin K-dependent carboxylation of synthetic Phe-Leu-Glu-Glu-Val by rat liver microsomes yields a secondary product, which has been identified as Leu-Gla-Glu-Val. Similar results are obtained with other synthetic substrates. The microsomal preparation has been shown to contain an aminopeptidase activity which splits carboxylation products and substrates but is unable to hydrolyse the Leu-Gla peptide bond.
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Vitamin K-dependent carboxylation. Study of the hydrogen abstraction stereochemistry with gamma-fluoroglutamic acid-containing peptides. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(20)81998-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Gaudry M, Bory S, Dubois J, Azerad R, Marquet A. Vitamin K dependent carboxylation: study of diastereoisomeric gamma-methylglutamic acid containing peptidic substrates. Biochem Biophys Res Commun 1983; 113:454-61. [PMID: 6870869 DOI: 10.1016/0006-291x(83)91747-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Two pentapeptides Phe-Leu-X-Glu-Val where X is either the L-threo-gamma-methylglutamic acid or the L-erythro isomer have been synthesized and tested as substrates in the vitamin K dependent carboxylation. The gamma-methylglutamic residue is not carboxylated and both peptides are inhibitors of the carboxylation of the reference peptide Phe-Leu-Glu-Glu-Val. The threo containing isomer has a much better affinity than the reference and is the best inhibitor of this reaction described so far.
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Abstract
In summary, in this review on the function of vitamin K in post-translational modification of precursor proteins by carboxylation of certain glutamyl residues, I have tried to cover in particular the recent work on the reaction, the enzymes involved and the mechanisms being considered. In doing this I have also considered vitamin K, its discovery, its functional form and the possible relation of its metabolism to the carboxylation reaction. Equally the various vitamin K-dependent gla-containing proteins currently known have been described. The carboxylation of synthetic small molecule exogenous substrates and the synthesis and metabolism of the products of carboxylation are of great help in studying the reaction. Structural specificity of vitamin K analogs in vivo and in vitro has been compared and the use of various antagonists in vivo and in vitro considered in attempts to gain an understanding of the overall reaction. The reactions subsequent to carboxylation, e.g., the activation of prothrombin to thrombin via serine proteases and the related activation of the other vitamin K-dependent proteins have not been considered in this review. The review has not covered prothrombin or other vitamin K-dependent protein isolation, nor the determination of these proteins. As the vitamin K-dependent protein carboxylation story has developed over the past six years, a number of reviews have been written which help in keeping up with the various aspects of the field as it has expanded. These reviews refer to many of the papers I have had to eliminate due to space limitations. They are referenced as 469-489. The review is in no sense comprehensive and many papers have been missed or only mentioned. I have tried to concentrate on the more recent work and, thus, much of the very fine work of the 1940's on vitamin K chemistry is hardly mentioned. Some redundancy has been built into the organization of the review so that a reader can obtain a reasonable view of any one section without having to search the whole review for all possible relevant information on any particular part of the field.
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Chander KS, Gaudry M, Marquet A, Rikong-Adie H, Decottignies-Lemarechal P, Azerad R. Effect of reduced vitamin K esters on vitamin K-dependent carboxylation. Biochim Biophys Acta Gen Subj 1981. [DOI: 10.1016/0304-4165(81)90321-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Wallin R, Suttie JW. Vitamin K-dependent carboxylase: possible artifact of analysis due to a pyridine nucleotide-dependent carboxylation. Biochem Biophys Res Commun 1980; 94:1374-80. [PMID: 7396966 DOI: 10.1016/0006-291x(80)90571-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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