Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Giardia intestinalis lacks the ability to synthesise deoxyribonucleotides de novo and must rely on salvage synthesis. Two separate kinases, specific for purines (deoxyadenosine and deoxyguanosine) and pyrimidines (thymidine and deoxycytidine), respectively, are responsible for the incorporation of deoxyribonucleosides. A substantial degree of purification was achieved for the purine deoxynucleoside kinase by the combination of Mono Q anion exchange chromatography, preparative gel electrophoresis and Superose 12 gel filtration. An overall recovery of 4%, with 186- and 174-fold purification, for deoxyguanosine kinase and deoxyadenosine kinase activities, respectively, was observed. The molecular weight was found to be approximately 80,000 by gel filtration. Only a partial purification of thymidine/deoxycytidine kinase was achieved. However, both pyrimidine activities remained associated throughout various purification procedures and appeared to be associated with a protein of 44 kDa.
Mol Biochem Parasitol 1993 Jul
PMID:Deoxynucleoside kinases of Giardia intestinalis. 839 5

Mycoplasmas are unable to synthesize purine and pyrimidine bases de novo. Therefore, salvage of existing nucleosides and bases is essential for their survival. Four mycoplasma species were studied with regard to their ability to phosphorylate deoxynucleosides. High levels of thymidine kinase (TK), deoxycytidine kinase (dCK), deoxyguanosine kinase (dGK) and deoxyadenosine kinase (dAK) activities were detected in extracts from Mycoplasma pneumoniae, Mycoplasma mycoides subsp. mycoides SC (M. mymySC), Acholeplasma laidlawii (A. laidlawii) and Mycoplasma arginini (M. arginini). Nucleoside phosphotransferase activities were found at high levels in A. laidlawii and low levels in M. arginini. Pyrophosphate-dependent deoxynucleoside kinase activities were detected mainly in A. laidlawii and M. mymySC extracts. Two open reading frames were identified in the M. mymySC genome; one showed 25% sequence identity to human dGK and the other one had about 26% sequence identity to human TK1. The M. mymySC dGK-like enzyme was cloned, expressed in Escherichia coli and affinity-purified. This enzyme phosphorylated dAdo, dGuo and dCyd, and the highest catalytic rate was with dAdo as substrate. Therefore, we suggest that this enzyme should be named deoxyadenosine kinase. The physiological role of mycoplasma dAK and TK may be to support the unusually large dATP and dTTP pools required for replication of mycoplasma genomes.
Mol Microbiol 2001 Nov
PMID:Novel deoxynucleoside-phosphorylating enzymes in mycoplasmas: evidence for efficient utilization of deoxynucleosides. 1173 47

Replacement of the Asp-84 residue of the deoxyguanosine kinase subunit of the tandem deoxyadenosine kinase/ deoxyguanosine kinase (dAK/dGK) from Lactobacillus acidophilus R-26 by Ala, Asn, or Glu produced increased Km values for deoxyguanosine on dGK. However, it did not seem to affect the binding of Mg-ATP. The Asp-84 dGK replacements had no apparent effect on the binding of deoxyadenosine by dAK. However, the mutant dGKs were no longer inhibited by dGTP, normally a potent distal endproduct inhibitor of dGK. Moreover, the allosteric activation of dAK activity by dGTP or dGuo was lost in the modified heterodimeric dAK/dGK enzyme. Therefore, it seems very likely that Asp-84 participates in dGuo binding at the active site of the dGK subunit of dAK/dGK from Lactobacillus acidophilus R-26.
J Biochem Mol Biol 2002 Mar 31
PMID:Mutations within the putative active site of heterodimeric deoxyguanosine kinase block the allosteric activation of the deoxyadenosine kinase subunit. 1229 37

Surface plasmon resonance (SPR) detection technology was employed to investigate the kinetic mechanism of deoxyadenosine kinase from Mycoplasma mycoides ssp. mycoides SC. In our experimental approach, the enzyme was attached to the sensor surface, the reactants were injected in the mobile phase, and the product-enzyme complex formation was measured using the fact that the rate of product formation exceeds that of its dissociation. The pre-steady-state analysis of deoxyguanosine phosphorylation showed the presence of a burst phase, which is consistent with product dissociation being a rate-limiting step. High activity of the immobilized enzyme was demonstrated by analyzing the reaction mixture eluted from the chip and by determining the Michaelis-Menten constants for several phosphate acceptors (e.g., deoxyadenosine) and phosphate donors (e.g., ATP) using SPR detection. These values were in good agreement with those reported previously [Wang, L. et al. (2001) Mol. Microbiol. 42, 1065-1073]. The bisubstrate initial rate pattern obtained was characteristic of a sequential kinetic mechanism. Because in the method applied here it is the mass change on the surface that is monitored, a new mathematical approach to interpreting product inhibition experiments was proposed. According to that approach, product inhibition studies, supported by product binding experiments, indicated that the reaction mechanism was of Bi Bi sequential ordered type, involving the formation of a ternary complex, in which ATP and deoxyadenosine bound sequentially, followed by a transfer of the phosphate group, and an ordered release of products with ADP dissociating before dAMP.
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PMID:Kinetic mechanism of deoxyadenosine kinase from Mycoplasma determined by surface plasmon resonance technology. 1640 Oct 80

Deoxyribonucleoside kinases (dNKs) catalyze the transfer of a phosphoryl group from ATP to a deoxyribonucleoside (dN), a key step in DNA precursor synthesis. Recently structural information concerning dNKs has been obtained, but no structure of a bacterial dCK/dGK enzyme is known. Here we report the structure of such an enzyme, represented by deoxyadenosine kinase from Mycoplasma mycoides subsp. mycoides small colony type (Mm-dAK). Superposition of Mm-dAK with its human counterpart's deoxyguanosine kinase (dGK) and deoxycytidine kinase (dCK) reveals that the overall structures are very similar with a few amino acid alterations in the proximity of the active site. To investigate the substrate specificity, Mm-dAK has been crystallized in complex with dATP and dCTP, as well as the products dCMP and dCDP. Both dATP and dCTP bind to the enzyme in a feedback-inhibitory manner with the dN part in the deoxyribonucleoside binding site and the triphosphates in the P-loop. Substrate specificity studies with clinically important nucleoside analogs as well as several phosphate donors were performed. Thus, in this study we combine structural and kinetic data to gain a better understanding of the substrate specificity of the dCK/dGK family of enzymes. The structure of Mm-dAK provides a starting point for making new anti bacterial agents against pathogenic bacteria.
J Mol Biol 2007 Mar 09
PMID:Structure-function analysis of a bacterial deoxyadenosine kinase reveals the basis for substrate specificity. 1722 40

The salvage of deoxyribonucleosides in the social amoeba Dictyostelium discoideum, which has an extremely A+T-rich genome, was investigated. All native deoxyribonucleosides were phosphorylated by D. discoideum cell extracts and we subcloned three deoxyribonucleoside kinase (dNK) encoding genes. D. discoideum thymidine kinase was similar to the human thymidine kinase 1 and was specific for thymidine with a K(m) of 5.1 microM. The other two cloned kinases were phylogenetically closer to bacterial deoxyribonucleoside kinases than to the eukaryotic enzymes. D. discoideum deoxyadenosine kinase (DddAK) had a K(m) for deoxyadenosine of 22.7 microM and a k(cat) of 3.7 s(-1) and could not efficiently phosphorylate any other native deoxyribonucleoside. D. discoideum deoxyguanosine kinase was also a purine-specific kinase and phosphorylated significantly only deoxyguanosine, with a K(m) of 1.4 microM and a k(cat) of 3 s(-1). The two purine-specific deoxyribonucleoside kinases could represent ancient enzymes present in the common ancestor of bacteria and eukaryotes but remaining only in a few eukaryote lineages. The narrow substrate specificity of the D. discoideum dNKs reflects the biased genome composition and we attempted to explain the strict preference of DddAK for deoxyadenosine by modeling the active center with different substrates. Apart from its native substrate, deoxyadenosine, DddAK efficiently phosphorylated fludarabine. Hence, DddAK could be used in the enzymatic production of fludarabine monophosphate, a drug used in the treatment of chronic lymphocytic leukemia.
J Mol Biol 2007 Jun 08
PMID:Dictyostelium discoideum salvages purine deoxyribonucleosides by highly specific bacterial-like deoxyribonucleoside kinases. 1744 96