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Nitzahn M, Lipshutz GS. CPS1: Looking at an ancient enzyme in a modern light. Mol Genet Metab 2020; 131:289-298. [PMID: 33317798 PMCID: PMC7738762 DOI: 10.1016/j.ymgme.2020.10.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/02/2020] [Accepted: 10/03/2020] [Indexed: 02/06/2023]
Abstract
The mammalian urea cycle (UC) is responsible for siphoning catabolic waste nitrogen into urea for excretion. Disruptions of the functions of any of the enzymes or transporters lead to elevated ammonia and neurological injury. Carbamoyl phosphate synthetase 1 (CPS1) is the first and rate-limiting UC enzyme responsible for the direct incorporation of ammonia into UC intermediates. Symptoms in CPS1 deficiency are typically the most severe of all UC disorders, and current clinical management is insufficient to prevent the associated morbidities and high mortality. With recent advances in basic and translational studies of CPS1, appreciation for this enzyme's essential role in the UC has been broadened to include systemic metabolic regulation during homeostasis and disease. Here, we review recent advances in CPS1 biology and contextualize them around the role of CPS1 in health and disease.
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Affiliation(s)
- Matthew Nitzahn
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Gerald S Lipshutz
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Psychiatry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Semel Institute for Neuroscience, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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2
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Abstract
One approach to bringing enzymes together for multienzyme biocatalysis is genetic fusion. This enables the production of multifunctional enzymes that can be used for whole-cell biotransformations or for in vitro (cascade) reactions. In some cases and in some aspects, such as expression and conversions, the fused enzymes outperform a combination of the individual enzymes. In contrast, some enzyme fusions are greatly compromised in activity and/or expression. In this Minireview, we give an overview of studies on fusions between two or more enzymes that were used for biocatalytic applications, with a focus on oxidative enzymes. Typically, the enzymes are paired to facilitate cofactor recycling or cosubstrate supply. In addition, different linker designs are briefly discussed. Although enzyme fusion is a promising tool for some biocatalytic applications, future studies could benefit from integrating the findings of previous studies in order to improve reliability and effectiveness.
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Affiliation(s)
- Friso S. Aalbers
- Molecular Enzymology GroupUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Marco W. Fraaije
- Molecular Enzymology GroupUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
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3
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Shi D, Caldovic L, Tuchman M. Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets. BIOLOGY 2018; 7:biology7020034. [PMID: 29895729 PMCID: PMC6022934 DOI: 10.3390/biology7020034] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/25/2018] [Accepted: 06/07/2018] [Indexed: 11/16/2022]
Abstract
Carbamyl phosphate (CP) is well-known as an essential intermediate of pyrimidine and arginine/urea biosynthesis. Chemically, CP can be easily synthesized from dihydrogen phosphate and cyanate. Enzymatically, CP can be synthesized using three different classes of enzymes: (1) ATP-grasp fold protein based carbamyl phosphate synthetase (CPS); (2) Amino-acid kinase fold carbamate kinase (CK)-like CPS (anabolic CK or aCK); and (3) Catabolic transcarbamylase. The first class of CPS can be further divided into three different types of CPS as CPS I, CPS II, and CPS III depending on the usage of ammonium or glutamine as its nitrogen source, and whether N-acetyl-glutamate is its essential co-factor. CP can donate its carbamyl group to the amino nitrogen of many important molecules including the most well-known ornithine and aspartate in the arginine/urea and pyrimidine biosynthetic pathways. CP can also donate its carbamyl group to the hydroxyl oxygen of a variety of molecules, particularly in many antibiotic biosynthetic pathways. Transfer of the carbamyl group to the nitrogen group is catalyzed by the anabolic transcarbamylase using a direct attack mechanism, while transfer of the carbamyl group to the oxygen group is catalyzed by a different class of enzymes, CmcH/NodU CTase, using a different mechanism involving a three-step reaction, decomposition of CP to carbamate and phosphate, transfer of the carbamyl group from carbamate to ATP to form carbamyladenylate and pyrophosphate, and transfer of the carbamyl group from carbamyladenylate to the oxygen group of the substrate. CP is also involved in transferring its phosphate group to ADP to generate ATP in the fermentation of many microorganisms. The reaction is catalyzed by carbamate kinase, which may be termed as catabolic CK (cCK) in order to distinguish it from CP generating CK. CP is a thermally labile molecule, easily decomposed into phosphate and cyanate, or phosphate and carbamate depending on the pH of the solution, or the presence of enzyme. Biological systems have developed several mechanisms including channeling between enzymes, increased affinity of CP to enzymes, and keeping CP in a specific conformation to protect CP from decomposition. CP is highly important for our health as both a lack of, or decreased, CP production and CP accumulation results in many disease conditions.
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Affiliation(s)
- Dashuang Shi
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA.
- Department of Genomics and Precision Medicine, The George Washington University, Washington, DC 20010, USA.
| | - Ljubica Caldovic
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA.
- Department of Genomics and Precision Medicine, The George Washington University, Washington, DC 20010, USA.
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA.
- Department of Genomics and Precision Medicine, The George Washington University, Washington, DC 20010, USA.
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4
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Specific discrimination of three pathogenic Salmonella enterica subsp. enterica serotypes by carB-based oligonucleotide microarray. Appl Environ Microbiol 2013; 80:366-73. [PMID: 24185846 DOI: 10.1128/aem.02978-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
It is important to rapidly and selectively detect and analyze pathogenic Salmonella enterica subsp. enterica in contaminated food to reduce the morbidity and mortality of Salmonella infection and to guarantee food safety. In the present work, we developed an oligonucleotide microarray containing duplicate specific capture probes based on the carB gene, which encodes the carbamoyl phosphate synthetase large subunit, as a competent biomarker evaluated by genetic analysis to selectively and efficiently detect and discriminate three S. enterica subsp. enterica serotypes: Choleraesuis, Enteritidis, and Typhimurium. Using the developed microarray system, three serotype targets were successfully analyzed in a range as low as 1.6 to 3.1 nM and were specifically discriminated from each other without nonspecific signals. In addition, the constructed microarray did not have cross-reactivity with other common pathogenic bacteria and even enabled the clear discrimination of the target Salmonella serotype from a bacterial mixture. Therefore, these results demonstrated that our novel carB-based oligonucleotide microarray can be used as an effective and specific detection system for S. enterica subsp. enterica serotypes.
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Lopes-Marques M, Igrejas G, Amorim A, Azevedo L. Human carbamoyl phosphate synthetase I (CPSI): insights on the structural role of the unknown function domains. Biochem Biophys Res Commun 2012; 421:409-12. [PMID: 22521883 DOI: 10.1016/j.bbrc.2012.04.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 04/05/2012] [Indexed: 10/28/2022]
Abstract
Carbamoyl phosphate synthetase (CPS) is an ancient protein. In mammals it intervenes in the urea cycle. This enzyme is organized into six domains, three of which have no established role in the mammalian enzyme. Taking advantage of the high degree of conservation between the human and the Escherichia coli homologue a comparative study was carried out in order to infer about the biological role of these less characterized domains. We show that among the residues involved in the maintenance of quaternary structure of the E. coli enzyme, several are highly conserved between human and bacterial enzyme and match the homologous positions of the "unknown function" domains in human enzyme, suggesting they are involved in the structural stability of the human enzyme as they are in bacteria.
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Affiliation(s)
- Monica Lopes-Marques
- IPATIMUP - Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal.
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Martínez AI, Pérez-Arellano I, Pekkala S, Barcelona B, Cervera J. Genetic, structural and biochemical basis of carbamoyl phosphate synthetase 1 deficiency. Mol Genet Metab 2010; 101:311-23. [PMID: 20800523 DOI: 10.1016/j.ymgme.2010.08.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 08/02/2010] [Accepted: 08/02/2010] [Indexed: 01/28/2023]
Abstract
Carbamoyl phosphate synthetase 1 (CPS1) plays a paramount role in liver ureagenesis since it catalyzes the first and rate-limiting step of the urea cycle, the major pathway for nitrogen disposal in humans. CPS1 deficiency (CPS1D) is an autosomal recessive inborn error which leads to hyperammonemia due to mutations in the CPS1 gene, or is caused secondarily by lack of its allosteric activator NAG. Proteolytic, immunological and structural data indicate that human CPS1 resembles Escherichia coli CPS in structure, and a 3D model of CPS1 has been presented for elucidating the pathogenic role of missense mutations. Recent availability of CPS1 expression systems also can provide valuable tools for structure-function analysis and pathogenicity-testing of mutations in CPS1. In this paper, we provide a comprehensive compilation of clinical CPS1 mutations, and discuss how structural knowledge of CPS enzymes in combination with in vitro analyses can be a useful tool for diagnosis of CPS1D.
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Affiliation(s)
- Ana Isabel Martínez
- Molecular Recognition Laboratory, Centro de Investigación Príncipe Felipe (CIPF) Valencia, Spain
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Meister A. Mechanism and regulation of the glutamine-dependent carbamyl phosphate synthetase of Escherichia coli. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 62:315-74. [PMID: 2658488 DOI: 10.1002/9780470123089.ch7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- A Meister
- Department of Biochemistry, Cornell University Medical College, New York, New York 10021
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8
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Serre V, Penverne B, Souciet JL, Potier S, Guy H, Evans D, Vicart P, Hervé G. Integrated allosteric regulation in the S. cerevisiae carbamylphosphate synthetase - aspartate transcarbamylase multifunctional protein. BMC BIOCHEMISTRY 2004; 5:6. [PMID: 15128434 PMCID: PMC434488 DOI: 10.1186/1471-2091-5-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Accepted: 05/05/2004] [Indexed: 11/24/2022]
Abstract
Background The S. cerevisiae carbamylphosphate synthetase – aspartate transcarbamylase multifunctional protein catalyses the first two reactions of the pyrimidine pathway. In this organism, these two reactions are feedback inhibited by the end product UTP. In the present work, the mechanisms of these integrated inhibitions were studied. Results The results obtained show that the inhibition is competitive in the case of carbamylphosphate synthetase and non-competitive in the case of aspartate transcarbamylase. They also identify the substrate whose binding is altered by this nucleotide and the step of the carbamylphosphate synthetase reaction which is inhibited. Furthermore, the structure of the domains catalyzing these two reactions were modelled in order to localize the mutations which, specifically, alter the aspartate transcarbamylase sensitivity to the feedback inhibitor UTP. Taken together, the results make it possible to propose a model for the integrated regulation of the two activities of the complex. UTP binds to a regulatory site located in the vicinity of the carbamylphosphate synthetase catalytic subsite which catalyzes the third step of this enzyme reaction. Through a local conformational change, this binding decreases, competitively, the affinity of this site for the substrate ATP. At the same time, through a long distance signal transmission process it allosterically decreases the affinity of the aspartate transcarbamylase catalytic site for the substrate aspartate. Conclusion This investigation provides informations about the mechanisms of allosteric inhibition of the two activities of the CPSase-ATCase complex. Although many allosteric monofunctional enzymes were studied, this is the first report on integrated allosteric regulation in a multifunctional protein. The positions of the point mutations which specifically abolish the sensitivity of aspartate transcarbamylase to UTP define an interface between the carbamylphosphate synthetase and aspartate transcarbamylase domains, through which the allosteric signal for the regulation of aspartate transcarbamylase must be propagated.
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Affiliation(s)
- Valérie Serre
- Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, FRE 2621 CNRS and Université Pierre et Marie Curie, 96 Bd Raspail 75006 Paris, France
- Laboratoire de Bioactivation des Peptides, Institut Jacques Monod, 2 Place Jussieu, 75251 Paris Cedex 05, France
| | - Bernadette Penverne
- Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, FRE 2621 CNRS and Université Pierre et Marie Curie, 96 Bd Raspail 75006 Paris, France
| | - Jean-Luc Souciet
- Laboratoire Dynamique et Expression des Génomes de Microorganismes, FRE 2326, Université Louis Pasteur/CNRS, 67083 Strasbourg Cedex, France
| | - Serge Potier
- Laboratoire Dynamique et Expression des Génomes de Microorganismes, FRE 2326, Université Louis Pasteur/CNRS, 67083 Strasbourg Cedex, France
| | - Hedeel Guy
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, 540 E. Canfield Street, Detroit, MI 48201, USA
| | - David Evans
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, 540 E. Canfield Street, Detroit, MI 48201, USA
| | - Patrick Vicart
- Laboratoire Cytosquelette et Développement, UMR 7000 CNRS and Université Pierre et Marie Curie, 105 Bd de l'Hôpital 75013 Paris, France
| | - Guy Hervé
- Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, FRE 2621 CNRS and Université Pierre et Marie Curie, 96 Bd Raspail 75006 Paris, France
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Evans DR, Guy HI. Mammalian pyrimidine biosynthesis: fresh insights into an ancient pathway. J Biol Chem 2004; 279:33035-8. [PMID: 15096496 DOI: 10.1074/jbc.r400007200] [Citation(s) in RCA: 291] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- David R Evans
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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10
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Moulton JK, Wiegmann BM. Evolution and phylogenetic utility of CAD (rudimentary) among Mesozoic-aged Eremoneuran Diptera (Insecta). Mol Phylogenet Evol 2004; 31:363-78. [PMID: 15019631 DOI: 10.1016/s1055-7903(03)00284-7] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2003] [Revised: 07/17/2003] [Indexed: 11/30/2022]
Abstract
We sequenced nearly the entire carbomoylphosphate synthase (CPS) domain of CAD, or rudimentary, (ca. 4 kb) from 29 species of flies representing all major clades within Eremoneura, or higher flies, and several orthorrhaphous brachyceran outgroups. We compared these sequences with orthologs from Anopheles gambiae and Drosophila melanogaster to assess structure, compositional bias, and phylogenetic utility. CAD is large (6.6+ kb), complex (comprised of three major and myriad minor functional domains) and relatively free of introns, extreme nucleotide bias (except third codon positions), and large hypervariable regions. The CPS domain possesses moderate levels of nonsynonymous divergence among taxa of intermediate evolutionary age and conveys considerable phylogenetic signal. Phylogenetic analysis of CPS sequences under varying methods and assumptions resulted in well-resolved, strongly supported trees concordant with many traditional ideas about higher dipteran phylogeny and with prior inferences from 28S rDNA. The most robustly supported major eremoneuran clades were Cyclorrhapha, Platypezoidea, Eumuscomorpha, Empidoidea, Atelestidae, Empidoidea exclusive of Atelestidae, Hybotidae s.l., Microphoridae+Dolichopodidae, and Empididae s. str. Because CAD is ubiquitous, apparently single copy (at least within holometabolous insects), readily obtained from several insect orders using primers described herein, and exhibits considerable phylogenetic utility, it should have wide applicability in insect molecular systematics.
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Affiliation(s)
- John K Moulton
- Department of Entomology and Plant Pathology, 2431 Center Drive, 205 Ellington Plant Sciences Building, The University of Tennessee, Knoxville, TN 37996-4560, USA.
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11
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Summar ML, Hall LD, Eeds AM, Hutcheson HB, Kuo AN, Willis AS, Rubio V, Arvin MK, Schofield JP, Dawson EP. Characterization of genomic structure and polymorphisms in the human carbamyl phosphate synthetase I gene. Gene 2003; 311:51-7. [PMID: 12853138 DOI: 10.1016/s0378-1119(03)00528-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Human carbamyl phosphate synthetase I (CPSI) is an essential hepatic enzyme that initiates the urea cycle. Deficiency of this enzyme usually results in lethal hyperammonemia. CPSI is encoded by the CPSI gene located on chromosome 2q35. In the present study, we report the coding sequence and define the intron-exon structure of the human CPSI gene. These data are compared to the previously defined rat CPSI gene structure. This work was generated from direct sequence determination of human genomic DNA (35 introns) and comparison to public domain sequence of anonymous BACs (2 introns). The human CPSI gene spans >120kb of genomic DNA. CPSI has 38 exons and 37 introns, and all adhere to the consensus splicing sequences. Comparison of the human and rat CPSI genes reveals that the nucleotide sequences, amino acid sequences, and intron-exon organizations are highly similar. We report the primers and conditions for screening the human CPSI exonic and bordering intronic sequences. We also screened 100 individuals for polymorphisms in the human CPSI gene and identified 14 polymorphisms in the CPSI message. The knowledge of the CPSI gene structure and the 14 polymorphisms presented in this study will greatly facilitate future molecular studies involving the CPSI gene and the enzyme it encodes.
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Affiliation(s)
- M L Summar
- Division of Medical Genetics, Vanderbilt University, Medical Center North DD2205, Nashville, TN 37232-2578, USA.
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12
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Ahuja A, Purcarea C, Guy HI, Evans DR. A novel carbamoyl-phosphate synthetase from Aquifex aeolicus. J Biol Chem 2001; 276:45694-703. [PMID: 11574542 DOI: 10.1074/jbc.m106382200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aquifex aeolicus, an extreme hyperthermophile, has neither a full-length carbamoyl-phosphate synthetase (CPSase) resembling the enzyme found in all mesophilic organisms nor a carbamate kinase-like CPSase such as those present in several hyperthermophilic archaea. However, the genome has open reading frames encoding putative proteins that are homologous to the major CPSase domains. The glutaminase, CPS.A, and CPS.B homologs from A. aeolicus were cloned, overexpressed in Escherichia coli, and purified to homogeneity. The isolated proteins could catalyze several partial reactions but not the overall synthesis of carbamoyl phosphate. However, a stable 124-kDa complex could be reconstituted from stoichiometric amounts of CPS.A and CPS.B proteins that synthesized carbamoyl phosphate from ATP, bicarbonate, and ammonia. The inclusion of the glutaminase subunit resulted in the formation of a 171-kDa complex that could utilize glutamine as the nitrogen-donating substrate, although the catalytic efficiency was significantly compromised. Molecular modeling, using E. coli CPSase as a template, showed that the enzyme has a similar structural organization and interdomain interfaces and that all of the residues known to be essential for function are conserved and properly positioned. A steady state kinetic study at 78 degrees C indicated that although the substrate affinity was similar for bicarbonate, ammonia, and glutamine, the K(m) for ATP was appreciably higher than that of any known CPSase. The A. aeolicus complex, with a split gene encoding the major synthetase domains and relatively inefficient coupling of amidotransferase and synthetase functions, may be more closely related to the ancestral precursor of contemporary mesophilic CPSases.
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Affiliation(s)
- A Ahuja
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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13
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Guy HI, Schmidt B, Hervé G, Evans DR. Pressure-induced dissociation of carbamoyl-phosphate synthetase domains. The catalytically active form is dimeric. J Biol Chem 1998; 273:14172-8. [PMID: 9603918 DOI: 10.1074/jbc.273.23.14172] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Carbamoyl-phosphate synthetase consists of an amidotransferase domain or subunit (GLN) that hydrolyzes glutamine and transfers the ammonia to the synthetase component (CPS) where the biosynthetic reaction occurs. The CPS domain is composed of two homologous subdomains, CPS.A and CPS.B, that catalyze different ATP-dependent reactions involved in carbamoyl phosphate synthesis. When the individual CPS.A and CPS.B subdomains were individually cloned and expressed in Escherichia coli (Guy, H. I., and Evans, D. R. (1996) J. Biol. Chem. 271, 13762-13769), they were found to be functionally equivalent and could each independently catalyze carbamoyl phosphate synthesis. The proposal was advanced that, although the monomers could catalyze the individual partial reactions, overall synthesis of carbamoyl phosphate required a homodimer of CPS.A or CPS.B. To test this hypothesis, the GLN-CPS.B dimer was reversibly dissociated at 1500 bar in a high pressure cell. Dissociation was accompanied by a loss of both glutamine- and ammonia-dependent CPSase activity. Activity was recovered once the protein was returned to atmospheric pressure. If the sample was cross-linked before exposure to high pressure, there was no dissociation and no loss of biosynthetic activity. In contrast, the bicarbonate-dependent ATPase and the carbamoyl phosphate-dependent ATP synthetase activities were largely unaffected by pressure-induced dissociation. These experiments confirmed the hypothesis that the synthesis of carbamoyl phosphate requires the concerted action of the two active sites within the homodimer.
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Affiliation(s)
- H I Guy
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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14
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Summar ML. Molecular genetic research into carbamoyl-phosphate synthase I: molecular defects and linkage markers. J Inherit Metab Dis 1998; 21 Suppl 1:30-9. [PMID: 9686343 DOI: 10.1023/a:1005349306311] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Deficiency of the hepatic enzyme carbamoyl-phosphate synthase I (CPSI), results in lethal or near-lethal hyperammonaemia. As part of our work on CPSI deficiency we have explored the development of markers for prenatal diagnosis, and the determination of molecular defects resulting in CPSI deficiency. We have determined a set of highly informative microsatellite markers flanking the CPSI gene. We have found 14 mutations in individuals with CPSI deficiency. During our mutation studies, we have made extensive use of cell lines not normally expressing CPSI through amplification of 'illegitimate' transcripts. We summarize these findings and review our current understanding of this important enzyme.
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Affiliation(s)
- M L Summar
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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15
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Guy HI, Bouvier A, Evans DR. The smallest carbamoyl-phosphate synthetase. A single catalytic subdomain catalyzes all three partial reactions. J Biol Chem 1997; 272:29255-62. [PMID: 9361005 DOI: 10.1074/jbc.272.46.29255] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Escherichia coli carbamoyl-phosphate synthetase (CPSase) is comprised of a 40-kDa glutaminase (GLN) and a 120-kDa synthetase (CPS) subunit. The CPS subunit consists of two homologous domains, CPS.A and CPS.B, which catalyze the two different ATP-dependent partial reactions involved in carbamoyl phosphate synthesis. Sequence similarities and controlled proteolysis experiments suggest that the CPS subdomains consist, in turn, of three subdomains, designated A1, A2, A3 and B1, B2, B3 for CPS.A and CPS.B, respectively. Previous studies of individually cloned CPS.A and CPS. B from E. coli and mammalian CPSase have shown that homologous dimers of either of these "half-molecules" could catalyze all three reactions involved in ammonia-dependent carbamoyl phosphate synthesis. Four smaller recombinant proteins were made for this study as follows: 1) A1-A2 in which the A3 subdomain was deleted from CPS.A, 2) B1-B2 lacking subdomain B3 of CPS.B, 3) the A2 subdomain of CPS.A, and 4) the B2 subdomain of CPS.B. When associated with the GLN subunit, A1-A2 and B1-B2 had both glutamine- and ammonia-dependent CPSase activities comparable to the wild-type protein. In contrast, the 27-kDa A2 and B2 recombinant proteins, which represent only 17% of the mass of the parent protein, were unable to use glutamine as a nitrogen donor, but the ammonia-dependent activity was enhanced 14-16-fold. The hyperactivity suggests that A2 and B2 are the catalytic subdomains and that A1 and B1 are attenuation domains which suppress the intrinsically high activity and are required for the physical association with the GLN subunit.
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Affiliation(s)
- H I Guy
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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Guy HI, Evans DR. Trapping an activated conformation of mammalian carbamyl-phosphate synthetase. J Biol Chem 1997; 272:19906-12. [PMID: 9242656 DOI: 10.1074/jbc.272.32.19906] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The amidotransferase or glutaminase domain (GLN domain) of mammalian carbamyl-phosphate synthetase II (CPSase II) catalyzes glutamine hydrolysis and transfers ammonia to the synthetase domain (CPS domain), where carbamyl phosphate formation is catalyzed in three consecutive reactions. The GLN and CPS domains are part of a single polypeptide and are connected via a 29-amino acid chain segment (GC linker). In contrast, the two comparable domains of Escherichia coli CPSase are not fused, but are separate, noncovalently associated subunits. To establish the function of the GC linker in mammalian CPSase, it was deleted, and the two domains were directly fused. The deletion mutant not only catalyzed glutamine-dependent carbamyl phosphate synthesis, but was activated 10-fold relative to its wild-type counterpart. However, ammonia-dependent synthesis of carbamyl phosphate was abolished, indicating that ammonia no longer had access to the active site on the CPS domain. The mutant was still sensitive to inhibition by the allosteric effector UTP, but was no longer activated by the allosteric effector phosphoribosyl pyrophosphate, although evidence indicated that the latter could bind to the enzyme. The linker appears to serve as a spacer that allows the complex to cycle between two conformations, an open low activity form in which the ammonia site on the CPS domain is accessible and an activated conformation in which the ammonia generated in situ from glutamine is directly channeled to the CPS active site and access to exogenous ammonia is blocked.
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Affiliation(s)
- H I Guy
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Guy HI, Rotgeri A, Evans DR. Activation by fusion of the glutaminase and synthetase subunits of Escherichia coli carbamyl-phosphate synthetase. J Biol Chem 1997; 272:19913-8. [PMID: 9242657 DOI: 10.1074/jbc.272.32.19913] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Escherichia coli carbamyl-phosphate synthetase consists of two subunits that act in concert to synthesize carbamyl phosphate. The 40-kDa subunit is an amidotransferase (GLN subunit) that hydrolyzes glutamine and transfers ammonia to the 120-kDa synthetase subunit (CPS subunit). The enzyme can also catalyze ammonia-dependent carbamyl phosphate synthesis if provided with exogenous ammonia. In mammalian cells, homologous amidotransferase and synthetase domains are carried on a single polypeptide chain called CAD. Deletion of the 29-residue linker that bridges the GLN and CPS domains of CAD stimulates glutamine-dependent carbamyl phosphate synthesis and abolishes the ammonia-dependent reaction (Guy, H. I., and Evans, D. R. (1997) J. Biol. Chem. 272, 19906-19912), suggesting that the deletion mutant is trapped in a closed high activity conformation. Since the catalytic mechanisms of the mammalian and bacterial proteins are the same, we anticipated that similar changes in the function of the E. coli protein could be produced by direct fusion of the GLN and CPS subunits. A construct was made in which the intergenic region between the contiguous carA and carB genes was deleted and the sequences encoding the carbamyl-phosphate synthetase subunits were fused in frame. The resulting fusion protein was activated 10-fold relative to the native protein, was unresponsive to the allosteric activator ornithine, and could no longer use ammonia as a nitrogen donor. Moreover, the functional linkage that coordinates the rate of glutamine hydrolysis with the activation of bicarbonate was abolished, suggesting that the protein was locked in an activated conformation similar to that induced by the simultaneous binding of all substrates.
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Affiliation(s)
- H I Guy
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Korte JJ, Salo WL, Cabrera VM, Wright PA, Felskie AK, Anderson PM. Expression of carbamoyl-phosphate synthetase III mRNA during the early stages of development and in muscle of adult rainbow trout (Oncorhynchus mykiss). J Biol Chem 1997; 272:6270-7. [PMID: 9045644 DOI: 10.1074/jbc.272.10.6270] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
It has been reported that the activities of the urea cycle-related enzymes ornithine carbamoyltransferase and carbamoyl-phosphate synthetase III (CPSase III) are induced during early life stages of ammonotelic rainbow trout (Oncorhynchus mykiss), suggesting that the urea cycle may play a physiological role in early development in teleost fish (Wright, P. A., Felskie, A., and Anderson, P. M. (1995) J. Exp. Biol. 198, 127-135). CPSase III cDNA prepared from embryo mRNA was sequenced, confirming the existence of the CPSase III gene in trout and its expression. The deduced amino acid sequence of the CPSase III is homologous to other CPSases. Supporting evidence for the expression of CPSase III activity in trout embryos was obtained by demonstrating expression of CPSase III mRNA as early as day 3 post-fertilization, reaching a maximum at 10-14 days, declining to a minimum at day 70, and then increasing to a relatively constant level from days 90 to 110 (relative to total RNA). Unexpectedly, in tissues of adult and fingerling trout, CPSase III mRNA was found to be present in muscle but not in other tissues, including liver. This finding was confirmed by assay of extracts, which showed CPSase III and ornithine carbamoyltransferase activity in muscle but not in other tissues. The pyrimidine nucleotide pathway-related CPSase II mRNA was expressed in all tissues.
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Affiliation(s)
- J J Korte
- Department of Biochemistry and Molecular Biology, University of Minnesota-Duluth, Duluth, Minnesota 55812, USA
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19
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van den Hoff MJ, Jonker A, Beintema JJ, Lamers WH. Evolutionary relationships of the carbamoylphosphate synthetase genes. J Mol Evol 1995; 41:813-32. [PMID: 8587126 DOI: 10.1007/bf00173161] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Carbamoylphosphate is a common intermediate in the metabolic pathways leading to the biosynthesis of arginine and pyrimidines. The amino acid sequences of all available proteins that catalyze the formation of carbamoylphosphate were retrieved from Genbank and aligned to estimate their mutual phylogenetic relations. In gram-negative bacteria carbamoylphosphate is synthesized by a two-subunit enzyme with glutaminase and carbamoylphosphate synthetase (CPS) activity, respectively. In gram-positive bacteria and lower eukaryotes this two-subunit CPS has become dedicated to arginine biosynthesis, while in higher eukaryotes the two subunits fused and subsequently lost the glutaminase activity. The CPS dedicated to pyrimidine synthesis is part of a multifunctional enzyme (CPS II), encoding in addition dihydroorotase and aspartate transcarbamoylase. Evidence is presented to strengthen the hypothesis that the two "kinase" subdomains of all CPS isozymes arose from a duplication of an ancestral gene in the progenote. A further duplication of the entire CPS gene occurred after the divergence of the plants and before the divergence of the fungi from the eukaryotic root, generating the two isoenzymes involved in either the synthesis of arginine or that of pyrimidines. The mutation rate was found to be five- to tenfold higher after the duplication than before, probably reflecting optimization of the enzymes for their newly acquired specialized function. We hypothesize that this duplication arose from a need for metabolic channeling for pyrimidine biosynthesis as it was accompanied by the tagging of the CPS gene with the genes for dihydroorotase and aspartate transcarbamoylase, and as the duplication occurred independently also in gram-positive bacteria. Analysis of the exon-intron organization of the two "kinase" subdomains in CPS I and II suggests that ancient exons may have comprised approx. 19 amino acids, in accordance with the prediction of the "intron-early" theory.
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Affiliation(s)
- M J van den Hoff
- Department of Anatomy and Embryology, University of Amsterdam, The Netherlands
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Reiser J, Glumoff V, Ochsner UA, Fiechter A. Molecular analysis of the Trichosporon cutaneum DSM 70698 argA gene and its use for DNA-mediated transformations. J Bacteriol 1994; 176:3021-32. [PMID: 8188603 PMCID: PMC205460 DOI: 10.1128/jb.176.10.3021-3032.1994] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Genomic clones capable of complementing a previously isolated arginine auxotrophic mutant strain of the filamentous yeast Trichosporon cutaneum DSM 70698 have been identified by DNA-mediated transformation, and a complementing 4,082-bp subfragment was sequenced. This analysis revealed an intact gene (arg4) showing a high degree of homology with the Saccharomyces cerevisiae CPA2 gene encoding the large subunit of carbamoyl-phosphate synthetase (CPS-A). The inferred amino acid sequence of the T. cutaneum argA-encoded protein contains 1,168 residues showing 62% identity with the sequence of the S. cerevisiae CPA2 protein, and the comparison of the two sequences uncovered a putative intron sequence of 81 nucleotides close to the 5' end of the coding region of the T. cutaneum argA gene. The presence of this intron was confirmed by nuclease protection studies and by direct DNA sequence analysis of a cDNA fragment which had been obtained by PCR amplification. The T. cutaneum intron shares the general characteristics of introns found in yeasts and filamentous fungi. A major transcript of around 4 kb was found in Northern (RNA) blots. The T. cutaneum argA coding region was expressed in Escherichia coli under the control of the regulatable tac promoter. A roughly 130-kDa protein which was found to cross-react with an anti-rat CPS antibody in Western blots (immunoblots) was observed. Two putative ATP-binding domains were identified, one in the amino-terminal half of the argA-encoded protein and the other in the carboxy-terminal half. These domains are highly conserved among the known CPS-A sequences from S. cerevisiae, E. coli, and the rat. From these results we conclude that the T. cutaneum argA gene encodes the large subunit of CPS. This is the first gene to be identified and analyzed in the T. cutaneum DSM 70698 strain.
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Affiliation(s)
- J Reiser
- Institut für Biotechnologie, ETH-Hönggerberg, Zürich, Switzerland
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21
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Helbing C, Atkinson B. 3,5,3'-Triiodothyronine-induced carbamyl-phosphate synthetase gene expression is stabilized in the liver of Rana catesbeiana tadpoles during heat shock. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32635-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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22
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Raushel FM, Miles BW, Post LE, David J. P. Mutational analysis of two putative domains within the large subunit of carbamoyl phosphate synthetase from escherichia coli. Bioorg Med Chem Lett 1992. [DOI: 10.1016/s0960-894x(01)80209-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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23
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Evolution of mitochondrial enzyme systems in fish: the mitochondrial synthesis of glutamine and citrulline. PHYLOGENETIC AND BIOCHEMICAL PERSPECTIVES 1991. [DOI: 10.1016/b978-0-444-89124-2.50007-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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24
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Urea synthesis in fishes: evolutionary and biochemical perspectives. PHYLOGENETIC AND BIOCHEMICAL PERSPECTIVES 1991. [DOI: 10.1016/b978-0-444-89124-2.50010-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Scofield MA, Lewis WS, Schuster SM. Nucleotide sequence of Escherichia coli asnB and deduced amino acid sequence of asparagine synthetase B. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38244-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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26
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Simmer JP, Kelly RE, Rinker AG, Scully JL, Evans DR. Mammalian carbamyl phosphate synthetase (CPS). DNA sequence and evolution of the CPS domain of the Syrian hamster multifunctional protein CAD. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)86959-9] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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27
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Rat C1-tetrahydrofolate synthase. cDNA isolation, tissue-specific levels of the mRNA, and expression of the protein in yeast. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39017-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Abstract
The functions and expression pattern of urea cycle enzymes have undergone considerable changes during the course of evolution. Sequence analyses shows that urea cycle enzymes from mammals are homologous to microbial enzymes of the arginine-metabolic pathway. Recently, an unexpected relationship was found between argininosuccinate lyase (EC 4.3.2.1), the fourth enzyme of the cycle, and delta-crystallin, a lens structural protein of birds and reptiles.
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Houghton JE, O'Donovan GA, Wild JR. Reconstruction of an enzyme by domain substitution effectively switches substrate specificity. Nature 1989; 338:172-4. [PMID: 2918938 DOI: 10.1038/338172a0] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The polar domains of the two transcarbamoylases, aspartate transcarbamoylase (ATCase) and ornithine transcarbamoylase, (OTCase) from Escherichia coli bind the common substrate carbamoyl phosphate and share extensive amino-acid sequence homology. The equatorial domains of the two enzymes differ in their substrate specificity (ATCase binds aspartate, OTCase binds ornithine) and have decreased sequence identity. While addressing the conservation of specific protein interactions during the evolution of these enzymes, we were able to switch one of their amino-acid-specific equatorial domains to produce a viable chimaeric enzyme. This was achieved by the in vitro fusion of DNA encoding the polar domain of OTCase to DNA encoding the equatorial domain of ATCase. The resulting gene fusion successfully transformed an argI-pyrB deletion strain of E. coli to pyrimidine prototrophy, giving rise to Pyr+ transformants that expressed ATCase but not OTCase activity. The formation of this active chimaeric enzyme shows that by exchanging protein domains between two functionally divergent enzymes we have achieved a switching in substrate specificity.
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Affiliation(s)
- J E Houghton
- Department of Biochemistry and Biophysics, Texas A & M University, College Station 77843
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31
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Abstract
Elasmobranch fishes, the coelacanth, estivating lungfish, amphibians, and mammals synthesize urea by the ornithine-urea cycle; by comparison, urea synthetic activity is generally insignificant in teleostean fishes. It is reported here that isolated liver cells of two teleost toadfishes, Opsanus beta and Opsansus tau, synthesize urea by the ornithine-urea cycle at substantial rates. Because toadfish excrete ammonia, do not use urea as an osmolyte, and have substantial levels of urease in their digestive systems, urea may serve as a transient nitrogen store, forming the basis of a nitrogen conservation shuttle system between liver and gut as in ruminants and hibernators. Toadfish synthesize urea using enzymes and subcellular distributions similar to those of elasmobranchs: glutamine-dependent carbamoyl phosphate synthethase (CPS III) and mitochondrial arginase. In contrast, mammals have CPS I (ammonia-dependent) and cytosolic arginase. Data on CPS and arginases in other fishes, including lungfishes and the coelacanth, support the hypothesis that the ornithine-urea cycle, a monophyletic trait in the vertebrates, underwent two key changes before the evolution of the extant lungfishes: a switch from CPS III to CPS I and replacement of mitochondrial arginase by a cytosolic equivalent.
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Affiliation(s)
- T P Mommsen
- Division of Biology and Living Resources, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, FL 33149
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Britton HG, Rubio V. Carbamoyl-phosphate synthetase I. Kinetics of binding and dissociation of acetylglutamate and of activation and deactivation. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 171:615-22. [PMID: 3345748 DOI: 10.1111/j.1432-1033.1988.tb13832.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The dissociation of the cofactor, acetylglutamate, from the enzyme-cofactor complex formed by carbamoyl-phosphate synthetase I of rat liver in the presence of ATP, Mg2+, K+ and HCO-3 has been studied by centrifugal gel filtration. The rate of its dissociation (k, 0.13 s-1) is considerably slower than the rate of enzyme turnover (approximately equal to 6 s-1) and it is not increased by ammonia, although ammonia reduces the rate of reassociation of the cofactor. Omission of ATP, Mg2+ or K+ from the column buffer leads to virtually complete dissociation of bound acetylglutamate during passage through the column (0.5-2 min), owing to an increase in dissociation and a decrease in reassociation, but reduction of free Mg2+ alone has the opposite action. Dilution of the enzyme-cofactor complex into a large volume of buffer causes a biphasic loss of enzyme activity with a t1/2 of the first phase comparable with that of the dissociation of acetylglutamate. These findings show (a) that acetylglutamate does not dissociate with each turnover of the enzyme; (b) that there are rapid interactions between binding of acetylglutamate and ATPA (ATPA yields Pi in the overall reaction), Mg2+ and K+, suggesting that these ligands bind in close proximity; and (c) that the enzyme transiently retains considerable activity after dissociation of the cofactor.
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Affiliation(s)
- H G Britton
- Instituto de Investigaciones Citologicas de la Caja de Ahorros de Valencia, Spain
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Benner S, Ellington AD. Interpreting the behavior of enzymes: purpose or pedigree? CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1988; 23:369-426. [PMID: 3067974 DOI: 10.3109/10409238809082549] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
To interpret the growing body of data describing the structural, physical, and chemical behaviors of biological macromolecules, some understanding must be developed to relate these behaviors to the evolutionary processes that created them. Behaviors that are the products of natural selection reflect biological function and offer clues to the underlying chemical principles. Nonselected behaviors reflect historical accident and random drift. This review considers experimental data relevant to distinguishing between nonfunctional and functional behaviors in biological macromolecules. In the first segment, tools are developed for building functional and historical models to explain macromolecular behavior. These tools are then used with recent experimental data to develop a general outline of the relationship between structure, behavior, and natural selection in proteins and nucleic acids. In segments published elsewhere, specific functional and historical models for three properties of enzymes--kinetics, stereospecificity, and specificity for cofactor structures--are examined. Functional models appear most suitable for explaining the kinetic behavior of proteins. A mixture of functional and historical models appears necessary to understand the stereospecificity of enzyme reactions. Specificity for cofactor structures appears best understood in light of purely historical models based on a hypothesis of an early form of life exclusively using RNA catalysis.
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Affiliation(s)
- S Benner
- Organische Chemie, Eidgenössische Technische Hochschule, Zürich, Switzerland
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Rubino SD, Nyunoya H, Lusty CJ. Catalytic domains of carbamyl phosphate synthetase. Glutamine-hydrolyzing site of Escherichia coli carbamyl phosphate synthetase. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67386-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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36
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Carrey EA. Nucleotide ligands protect the inter-domain regions of the multifunctional polypeptide CAD against limited proteolysis, and also stabilize the thermolabile part-reactions of the carbamoyl-phosphate synthase II domains within the CAD polypeptide. Biochem J 1986; 236:327-35. [PMID: 3638965 PMCID: PMC1146844 DOI: 10.1042/bj2360327] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Improved methodologies are described which allow the measurement of the part-reactions, with glutamine or ammonia as nitrogen donor, of mammalian carbamoyl-phosphate synthase II (EC 6.3.5.5) through the incorporation of [14C]bicarbonate into either carbamoyl phosphate or carbamoylaspartate. The enzyme is part of the multifunctional polypeptide (CAD) which also comprises the pyrimidine-biosynthetic enzymes aspartate transcarbamoylase (EC 2.1.3.2) and dihydro-orotase (EC 3.5.2.3). The conformational stability of the carbamoyl-phosphate synthase was investigated through the inactivation of the part-reactions which occurred during incubation at 37 degrees C. The domain involved in the removal of the amide N from glutamine was more thermolabile than the ammonia-dependent synthase moiety. The former activity was stabilized in the presence of sodium aspartate or MgATP, whereas the latter was stabilized by MgATP and MgUTP. Binding of MgUTP and MgATP to CAD restricted the initial proteolysis by trypsin and elastase of one or both regions linking the carbamoyl-phosphate synthase domain to the other major domains. A model is described to account for both aspects of nucleotide binding to CAD; these stabilizing effects may be important in the cell, where similar concentrations of nucleotides are found.
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Nyunoya H, Broglie KE, Widgren EE, Lusty CJ. Characterization and derivation of the gene coding for mitochondrial carbamyl phosphate synthetase I of rat. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39371-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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