The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Anna Karlsson - One of the best experts on this subject based on the ideXlab platform.
-
The many isoforms of human adenylate Kinases
The International Journal of Biochemistry & Cell Biology, 2014Co-Authors: Christakis Panayiotou, Nicola Solaroli, Anna KarlssonAbstract:Adenine nucleotides are involved in a variety of cellular metabolic processes, including nucleic acid synthesis and repair, formation of coenzymes, energy transfer, cell and ciliary motility, hormone secretion, gene expression regulation and ion-channel control. Adenylate Kinases are abundant phosphotransferases that catalyze the interconversion of adenine nucleotides and thus regulate the adenine nucleotide ratios in different intracellular compartments. Nine different adenylate Kinase isoenzymes have been identified and characterized so far in human tissues, named AK1 to AK9 according to their order of discovery. Adenylate Kinases differ in molecular weight, tissue distribution, subcellular localization, substrate and phosphate donor specificity and kinetic properties. The preferred substrate and phosphate donor of all adenylate Kinases are AMP and ATP respectively, but some members of the family can phosphorylate other substrates and use other phosphate donors. In addition to their Nucleoside Monophosphate Kinase activity, adenylate Kinases were found to possess Nucleoside diphosphate Kinase activity as they are able to phosphorylate both riboNucleoside and deoxyriboNucleoside diphosphates to their corresponding triphosphates. Nucleoside analogues are structural analogues of natural Nucleosides, used in the treatment of cancer and viral infections. They are inactive prodrugs that are dependent on intracellular phosphorylation to their pharmacologically active triphosphate form. Novel data presented in this review confirm the role of adenylate Kinases in the activation of deoxyadenosine and deoxycytidine Nucleoside analogues.
-
human ump cmp Kinase 2 a novel Nucleoside Monophosphate Kinase localized in mitochondria
Journal of Biological Chemistry, 2008Co-Authors: Yunjian Xu, Magnus Johansson, Anna KarlssonAbstract:Abstract Enzyme deficiency in the salvage pathway of deoxyribonucleotide synthesis in mitochondria can cause mtDNA depletion syndromes. We have identified a human mitochondrial UMP-CMP Kinase (UMP-CMPK, cytidylate Kinase; EC 2.7.4.14), designated as UMP-CMP Kinase 2 (UMP-CMPK2). The C-terminal domain of this 449-amino acid protein contains all consensus motifs of a Nucleoside Monophosphate Kinase. Phylogenetic analysis showed that UMP-CMPK2 belonged to a novel Nucleoside Monophosphate Kinase family, which was closer to thymidylate Kinase than to cytosolic UMP-CMP Kinase. Subcellular localization with green fluorescent protein fusion proteins illustrated that UMP-CMPK2 was localized in the mitochondria of HeLa cells and that the mitochondrial targeting signal was included in the N-terminal 22 amino acids. The enzyme was able to phosphorylate dUMP, dCMP, CMP, and UMP with ATP as phosphate donor, but the kinetic properties were different compared with the cytosolic UMP-CMPK. Its efficacy to convert dUMP was highest, followed by dCMP, whereas CMP and UMP were the poorest substrates. It also phosphorylated the Monophosphate forms of the Nucleoside analogs ddC, dFdC, araC, BVDU, and FdUrd, which suggests that UMP-CMPK2 may be involved in mtDNA depletion caused by long term treatment with ddC or other pyrimidine analogs. UMP-CMPK2 mRNA expression was exclusively detected in chronic myelogenous leukemia K-562 and lymphoblastic leukemia MOLT-4 among eight studied cancer cell lines. Particular high expression in leukemia cells, dominant expression in bone marrow, and tight correlation with macrophage activation and inflammatory response suggest that UMP-CMPK2 may have other functions in addition to the supply of substrates for mtDNA synthesis.
-
The Drosophila melanogaster UMP-CMP Kinase cDNA encodes an N-terminal mitochondrial import signal ☆ ☆☆
Biochemical and Biophysical Research Communications, 2003Co-Authors: Sophie Curbo, Magnus Johansson, Marjan Amiri, Fariba Foroogh, Anna KarlssonAbstract:Abstract Drosophila melanogaster cells express a multi-substrate deoxyriboNucleoside Kinase that phosphorylates both purine and pyrimidine deoxyriboNucleosides. The subsequent phosphorylation step is catalyzed by Nucleoside Monophosphate Kinases. We have cloned and characterized the D. melanogaster UMP-CMP Kinase ( Dm .UMP-CMP Kinase) to further study the nucleotide metabolizing enzymes in these cells. The Kinase, encoded by the dak1 gene, was ≈60% similar to the human UMP-CMP Kinase and predominantly phosphorylated CMP, dCMP, and UMP. Expression analysis showed that the Dm .UMP-CMP Kinase mRNA was constitutively expressed throughout the Drosophila development. The open-reading frame of the Dm. UMP-CMP Kinase cDNA was extended in the 5 ′ -region compared to UMP-CMP Kinases of other species. The extended region encoded an N-terminal sequence with properties characteristic of a mitochondrial import signal. Expression of the enzyme in fusion with the green fluorescent protein verified that the N-terminal signal targeted the enzyme to mitochondria. This is the first time a mitochondrial pyrimidine Nucleoside Monophosphate Kinase has been cloned from any organism and we discuss the implication of this finding for deoxyriboNucleoside salvage in both Drosophila and other organisms.
David Leroy Anton - One of the best experts on this subject based on the ideXlab platform.
-
enzymatic synthesis of cytidine 5 diphosphate using pyrimidine Nucleoside Monophosphate Kinase
Enzyme and Microbial Technology, 1990Co-Authors: John E Seip, Susan K Fager, R Grosz, John E Gavagan, Robert Dicosimo, David Leroy AntonAbstract:Abstract Nucleoside Monophosphate Kinase (NMPK, EC 2.7.4.4, from bovine liver or yeast) has been used to prepare cytidine 5′-diphosphate (CDP). The enzyme catalyses the reversible (Keq ≅ 1) reaction of a pyrimidine Nucleoside 5′-Monophosphate and ATP to produce a Nucleoside 5′-diphosphate and ADP. Equilibrium mixtures of CMP, CDP, ADP, and ATP were obtained from the reaction of CMP, ATP, and magnesium chloride with NMPK. The soluble enzyme could be recovered and reused but an enzyme activity half-life of only ca. 2 days was observed. Stabilization of enzyme activity by immobilization via covalent bonding to a carrier surface, and by gel entrapment, was examined. Immobilization yields were optimized by varying protein loading, pH, temperature, ionic strength, type of buffer, and concentration of enzyme substrates. The highest yields of immobilized NMPK activity were obtained by gel entrapment in a poly(acrylamide-co-N-acryloxysuccinimide) gel crosslinked with triethylenetetramine (PAN-500); NMPK immobilized using this method exhibited increased stability of enzyme activity compared to the unimmobilized enzyme.
Emil Alexov - One of the best experts on this subject based on the ideXlab platform.
-
banmoki a searchable database of homology based 3d models and their electrostatic properties of five bacterial Nucleoside Monophosphate Kinase families
International Journal of Biological Macromolecules, 2007Co-Authors: Petras J Kundrotas, Paulina Georgieva, Alexandra Shosheva, Petya Christova, Emil AlexovAbstract:Abstract The Nucleoside Monophosphate Kinases (NMPK) are important enzymes that control the ratio of mono- and di-phosphate Nucleosides and participate in gene regulation and signal transduction in the cell. However, despite their importance only several 3D structures were experimentally determined in contrast to the wealth of sequences available for each of the NMPK families. To fill this gap we present a Web-based database containing structural models for all proteins of the five bacterial Nucleoside Monophosphate Kinase (bNMPK) families. The models were computed by means of homology-based approach using a few experimentally determined bNMPK structures. The database also contains p K a values and their components calculated for the homology-based 3D models, which is a unique feature of the database. The BActerial Nucleoside Monophosphate Kinases (BANMOKI) database is freely accessible ( http://www.ces.clemson.edu/compbio/banmoki ) and offers an easy user-friendly interface for browsing, searching and downloading content of the database. The users can investigate, using the searching tools of the database, the properties of the bNMP Kinases in respect to sequence composition, electrostatic interactions and structural differences.
-
assessing the quality of the homology modeled 3d structures from electrostatic standpoint test on bacterial Nucleoside Monophosphate Kinase families
Journal of Bioinformatics and Computational Biology, 2007Co-Authors: Petras J Kundrotas, Paulina Georgieva, Alexandra Shosheva, Petya Christova, Emil AlexovAbstract:In this study, we address the issue of performing meaningful pKa calculations using homology modeled three-dimensional (3D) structures and analyze the possibility of using the calculated pKa values to detect structural defects in the models. For this purpose, the 3D structure of each member of five large protein families of a bacterial Nucleoside Monophosphate Kinases (NMPK) have been modeled by means of homology-based approach. Further, we performed pKa calculations for the each model and for the template X-ray structures. Each bacterial NMPK family used in the study comprised on average 100 members providing a pool of sequences and 3D models large enough for reliable statistical analysis. It was shown that pKa values of titratable groups, which are highly conserved within a family, tend to be conserved among the models too. We demonstrated that homology modeled structures with sequence identity larger than 35% and gap percentile smaller than 10% can be used for meaningful pKa calculations. In addition, it was found that some highly conserved titratable groups either exhibit large pKa fluctuations among the models or have pKa values shifted by several pH units with respect to the pKa calculated for the X-ray structure. We demonstrated that such case usually indicates structural errors associated with the model. Thus, we argue that pKa calculations can be used for assessing the quality of the 3D models by monitoring fluctuations of the pKa values for highly conserved titratable residues within large sets of homologous proteins.
John E Seip - One of the best experts on this subject based on the ideXlab platform.
-
enzymatic synthesis of cytidine 5 diphosphate using pyrimidine Nucleoside Monophosphate Kinase
Enzyme and Microbial Technology, 1990Co-Authors: John E Seip, Susan K Fager, R Grosz, John E Gavagan, Robert Dicosimo, David Leroy AntonAbstract:Abstract Nucleoside Monophosphate Kinase (NMPK, EC 2.7.4.4, from bovine liver or yeast) has been used to prepare cytidine 5′-diphosphate (CDP). The enzyme catalyses the reversible (Keq ≅ 1) reaction of a pyrimidine Nucleoside 5′-Monophosphate and ATP to produce a Nucleoside 5′-diphosphate and ADP. Equilibrium mixtures of CMP, CDP, ADP, and ATP were obtained from the reaction of CMP, ATP, and magnesium chloride with NMPK. The soluble enzyme could be recovered and reused but an enzyme activity half-life of only ca. 2 days was observed. Stabilization of enzyme activity by immobilization via covalent bonding to a carrier surface, and by gel entrapment, was examined. Immobilization yields were optimized by varying protein loading, pH, temperature, ionic strength, type of buffer, and concentration of enzyme substrates. The highest yields of immobilized NMPK activity were obtained by gel entrapment in a poly(acrylamide-co-N-acryloxysuccinimide) gel crosslinked with triethylenetetramine (PAN-500); NMPK immobilized using this method exhibited increased stability of enzyme activity compared to the unimmobilized enzyme.
Yunjian Xu - One of the best experts on this subject based on the ideXlab platform.
-
human ump cmp Kinase 2 a novel Nucleoside Monophosphate Kinase localized in mitochondria
Journal of Biological Chemistry, 2008Co-Authors: Yunjian Xu, Magnus Johansson, Anna KarlssonAbstract:Abstract Enzyme deficiency in the salvage pathway of deoxyribonucleotide synthesis in mitochondria can cause mtDNA depletion syndromes. We have identified a human mitochondrial UMP-CMP Kinase (UMP-CMPK, cytidylate Kinase; EC 2.7.4.14), designated as UMP-CMP Kinase 2 (UMP-CMPK2). The C-terminal domain of this 449-amino acid protein contains all consensus motifs of a Nucleoside Monophosphate Kinase. Phylogenetic analysis showed that UMP-CMPK2 belonged to a novel Nucleoside Monophosphate Kinase family, which was closer to thymidylate Kinase than to cytosolic UMP-CMP Kinase. Subcellular localization with green fluorescent protein fusion proteins illustrated that UMP-CMPK2 was localized in the mitochondria of HeLa cells and that the mitochondrial targeting signal was included in the N-terminal 22 amino acids. The enzyme was able to phosphorylate dUMP, dCMP, CMP, and UMP with ATP as phosphate donor, but the kinetic properties were different compared with the cytosolic UMP-CMPK. Its efficacy to convert dUMP was highest, followed by dCMP, whereas CMP and UMP were the poorest substrates. It also phosphorylated the Monophosphate forms of the Nucleoside analogs ddC, dFdC, araC, BVDU, and FdUrd, which suggests that UMP-CMPK2 may be involved in mtDNA depletion caused by long term treatment with ddC or other pyrimidine analogs. UMP-CMPK2 mRNA expression was exclusively detected in chronic myelogenous leukemia K-562 and lymphoblastic leukemia MOLT-4 among eight studied cancer cell lines. Particular high expression in leukemia cells, dominant expression in bone marrow, and tight correlation with macrophage activation and inflammatory response suggest that UMP-CMPK2 may have other functions in addition to the supply of substrates for mtDNA synthesis.
