- carba Nicotinamide Adenine Dinucleotide Phosphate: Robust Cofactor for Redox Biocatalysis
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Here we report a new robust nicotinamide dinucleotide phosphate cofactor analog (carba-NADP+) and its acceptance by many enzymes in the class of oxidoreductases. Replacing one ribose oxygen with a methylene group of the natural NADP+ was found to enhance stability dramatically. Decomposition experiments at moderate and high temperatures with the cofactors showed a drastic increase in half-life time at elevated temperatures since it significantly disfavors hydrolysis of the pyridinium-N?glycoside bond. Overall, more than 27 different oxidoreductases were successfully tested, and a thorough analytical characterization and comparison is given. The cofactor carba-NADP+ opens up the field of redox-biocatalysis under harsh conditions.
- D?ring, Manuel,Sieber, Volker,Simon, Robert C.,Tafertshofer, Georg,Zachos, Ioannis
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supporting information
p. 14701 - 14706
(2021/05/13)
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- Kinetic and mechanistic characterization of the glyceraldehyde 3-phosphate dehydrogenase from Mycobacterium tuberculosis
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Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a glycolytic protein responsible for the conversion of glyceraldehyde 3-phosphate (G3P), inorganic phosphate and nicotinamide adenine dinucleotide (NAD+) to 1,3-bisphosphoglycerate (1,3-BPG) and the reduced form of nicotinamide adenine dinucleotide (NADH). Here we report the characterization of GAPDH from Mycobacterium tuberculosis (Mtb). This enzyme exhibits a kinetic mechanism in which first NAD+, then G3P bind to the active site resulting in the formation of a covalently bound thiohemiacetal intermediate. After oxidation of the thiohemiacetal and subsequent nucleotide exchange (NADH off, NAD+ on), the binding of inorganic phosphate and phosphorolysis yields the product 1,3-BPG. Mutagenesis and iodoacetamide (IAM) inactivation studies reveal the conserved C158 to be responsible for nucleophilic catalysis and that the conserved H185 to act as a catalytic base. Primary, solvent and multiple kinetic isotope effects revealed that the first half-reaction is rate limiting and utilizes a step-wise mechanism for thiohemiacetal oxidation via a transient alkoxide to promote hydride transfer and thioester formation.
- Wolfson-Stofko, Brett,Hadi, Timin,Blanchard, John S.
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- Broad specificity of human phosphoglycerate kinase for antiviral nucleoside analogs
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Nucleoside analogs used in antiviral therapies need to be phosphorylated to their tri-phospho counterparts in order to be active on their cellular target. Human phosphoglycerate kinase (hPGK) was recently reported to participate in the last step of phosphorylation of cytidine l-nucleotide derivatives [Krishnan PGE, Lam W, Dutschman GE, Grill SP, Cheng YC. Novel role of 3-phosphoglycerate kinase, a glycolytic enzyme, in the activation of l-nucleoside analogs, a new class of anticancer and antiviral agents. J Biol Chem 2003;278:36726-32]. In the present work, we extended the enzymatic study of human PGK specificity to purine and pyrimidine nucleotide derivatives in both d- and l-configuration. Human PGK demonstrated catalytic efficiencies in the 104-10 5 M-1 s-1 range for purine ribo-, deoxyribo- and dideoxyribonucleotide derivatives, either in d- or l-configuration. In contrast, it was poorly active with natural pyrimidine d-nucleotides (less than 103 M-1 s-1). Pyrimidine l-enantiomers, which are promising therapeutic analogs against B hepatitis, were 2-25 times better substrates than their d-counterparts. The broad specificity of substrate of human PGK suggests that this enzyme may be involved in the cellular activation of several antiviral nucleoside analogs including dideoxyinosine, acyclovir, l-2′-deoxycytosine and l-2′-deoxythymidine.
- Gallois-Montbrun, Sarah,Faraj, Abdesslem,Seclaman, Edward,Sommadossi, Jean-Pierre,Deville-Bonne, Dominique,Véron, Michel
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p. 1749 - 1756
(2007/10/03)
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