Diphosphates: Inorganic salts of phosphoric acid that contain two phosphate groups.Cytidine Diphosphate: Cytidine 5'-(trihydrogen diphosphate). A cytosine nucleotide containing two phosphate groups esterified to the sugar moiety. Synonyms: CRPP; cytidine pyrophosphate.Polyribonucleotide Nucleotidyltransferase: An enzyme of the transferase class that catalyzes the reaction RNA(n+1) and orthophosphate to yield RNA(n) and a nucleoside diphosphate, or the reverse reaction. ADP, IDP, GDP, UDP, and CDP can act as donors in the latter case. (From Dorland, 27th ed) EC 2.7.7.8.Nucleoside-Diphosphate Kinase: An enzyme that is found in mitochondria and in the soluble cytoplasm of cells. It catalyzes reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside diphosphate, e.g., UDP, to form ADP and UTP. Many nucleoside diphosphates can act as acceptor, while many ribo- and deoxyribonucleoside triphosphates can act as donor. EC 2.7.4.6.Polyisoprenyl Phosphates: Phosphoric or pyrophosphoric acid esters of polyisoprenoids.Alkyl and Aryl Transferases: A somewhat heterogeneous class of enzymes that catalyze the transfer of alkyl or related groups (excluding methyl groups). EC 2.5.Uridine Diphosphate: A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety.Dimethylallyltranstransferase: An enzyme that, in the pathway of cholesterol biosynthesis, catalyzes the condensation of isopentenyl pyrophosphate and dimethylallylpyrophosphate to yield pyrophosphate and geranylpyrophosphate. The enzyme then catalyzes the condensation of the latter compound with another molecule of isopentenyl pyrophosphate to yield pyrophosphate and farnesylpyrophosphate. EC 2.5.1.1.Nucleotides: The monomeric units from which DNA or RNA polymers are constructed. They consist of a purine or pyrimidine base, a pentose sugar, and a phosphate group. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Apyrase: A calcium-activated enzyme that catalyzes the hydrolysis of ATP to yield AMP and orthophosphate. It can also act on ADP and other nucleoside triphosphates and diphosphates. EC 3.6.1.5.Ribonucleoside Diphosphate Reductase: An enzyme of the oxidoreductase class that catalyzes the formation of 2'-deoxyribonucleotides from the corresponding ribonucleotides using NADPH as the ultimate electron donor. The deoxyribonucleoside diphosphates are used in DNA synthesis. (From Dorland, 27th ed) EC 1.17.4.1.Adenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.Ribonucleotide ReductasesRibonucleotides: Nucleotides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)Geranyltranstransferase: An enzyme involved in the MEVALONATE pathway, it catalyses the synthesis of farnesyl diphosphate from isopentenyl diphosphate and dimethylallyl diphosphate.Phosphotransferases (Phosphate Group Acceptor): A group of enzymes that catalyzes the transfer of a phosphate group onto a phosphate group acceptor. EC 2.7.4.Farnesyltranstransferase: An enzyme that catalyzes the synthesis of geranylgeranyl diphosphate from trans, trans-farnesyl diphosphate and isopentenyl diphosphate.Phosphoglycerate Kinase: An enzyme catalyzing the transfer of a phosphate group from 3-phospho-D-glycerate in the presence of ATP to yield 3-phospho-D-glyceroyl phosphate and ADP. EC 2.7.2.3.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Cytosine NucleotidesPyrophosphatases: A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.Kinetics: The rate dynamics in chemical or physical systems.Deoxyribonucleotides: A purine or pyrimidine base bonded to a DEOXYRIBOSE containing a bond to a phosphate group.Purine Nucleotides: Purines attached to a RIBOSE and a phosphate that can polymerize to form DNA and RNA.Nucleosides: Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Arguloida: An order of CRUSTACEA that are parasitic on freshwater fish.Guanosine Diphosphate: A guanine nucleotide containing two phosphate groups esterified to the sugar moiety.Transferases: Transferases are enzymes transferring a group, for example, the methyl group or a glycosyl group, from one compound (generally regarded as donor) to another compound (generally regarded as acceptor). The classification is based on the scheme "donor:acceptor group transferase". (Enzyme Nomenclature, 1992) EC 2.SesquiterpenesTerpenes: A class of compounds composed of repeating 5-carbon units of HEMITERPENES.Magnesium: A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Phosphates: Inorganic salts of phosphoric acid.NM23 Nucleoside Diphosphate Kinases: A family of nucleotide diphosphate kinases that play a role in a variety of cellular signaling pathways that effect CELL DIFFERENTIATION; CELL PROLIFERATION; and APOPTOSIS. They are considered multifunctional proteins that interact with a variety of cellular proteins and have functions that are unrelated to their enzyme activity.Acid Anhydride Hydrolases: A group of enzymes that catalyze the hydrolysis of diphosphate bonds in compounds such as nucleoside di- and tri-phosphates, and sulfonyl-containing anhydrides such as adenylylsulfate. (Enzyme Nomenclature, 1992) EC 3.6.Pyruvate Kinase: ATP:pyruvate 2-O-phosphotransferase. A phosphotransferase that catalyzes reversibly the phosphorylation of pyruvate to phosphoenolpyruvate in the presence of ATP. It has four isozymes (L, R, M1, and M2). Deficiency of the enzyme results in hemolytic anemia. EC 2.7.1.40.Oligonucleotides: Polymers made up of a few (2-20) nucleotides. In molecular genetics, they refer to a short sequence synthesized to match a region where a mutation is known to occur, and then used as a probe (OLIGONUCLEOTIDE PROBES). (Dorland, 28th ed)Adenosine Triphosphatases: A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.Organophosphorus Compounds: Organic compounds that contain phosphorus as an integral part of the molecule. Included under this heading is broad array of synthetic compounds that are used as PESTICIDES and DRUGS.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.Hydroxyurea: An antineoplastic agent that inhibits DNA synthesis through the inhibition of ribonucleoside diphosphate reductase.Phosphoric Monoester Hydrolases: A group of hydrolases which catalyze the hydrolysis of monophosphoric esters with the production of one mole of orthophosphate. EC 3.1.3.Guanine NucleotidesAdenosine Monophosphate: Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.Cations, Divalent: Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Allosteric Regulation: The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.Catalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Cafe-au-Lait Spots: Light brown pigmented macules associated with NEUROFIBROMATOSIS and Albright's syndrome (see FIBROUS DYSPLASIA, POLYOSTOTIC).Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Guanosine Triphosphate: Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Structure-Activity Relationship: The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.Potassium Channels: Cell membrane glycoproteins that are selectively permeable to potassium ions. At least eight major groups of K channels exist and they are made up of dozens of different subunits.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Models, Chemical: Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Enzyme Activation: Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Molecular Weight: The sum of the weight of all the atoms in a molecule.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.