A Specific Inorganic Triphosphatase from Nitrosomonas europaea
| Autor: | Edwin De Pauw, Tatiana Skarina, David Delvaux, O. Onopriyenko, Valérie Gabelica, Vladimir V. Lunin, Mamidanna R. V.S. Murty, Bernard Lakaye, Lucien Bettendorff, Gregory Kohn, Pierre Wins |
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| Rok vydání: | 2011 |
| Předmět: |
chemistry.chemical_classification
0303 health sciences biology 030302 biochemistry & molecular biology Cell Biology biology.organism_classification Biochemistry Enzyme structure Adenylyl cyclase 03 medical and health sciences chemistry.chemical_compound Enzyme Thiamine triphosphatase chemistry Nitrosomonas europaea Triphosphatase Molecular Biology Pyrophosphatases Thiamine triphosphate 030304 developmental biology |
| Zdroj: | Journal of Biological Chemistry. 286:34023-34035 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m111.233585 |
| Popis: | The CYTH superfamily of proteins is named after its two founding members, the CyaB adenylyl cyclase from Aeromonas hydrophila and the human 25-kDa thiamine triphosphatase. Because these proteins often form a closed β-barrel, they are also referred to as triphosphate tunnel metalloenzymes (TTM). Functionally, they are characterized by their ability to bind triphosphorylated substrates and divalent metal ions. These proteins exist in most organisms and catalyze different reactions depending on their origin. Here we investigate structural and catalytic properties of the recombinant TTM protein from Nitrosomonas europaea (NeuTTM), a 19-kDa protein. Crystallographic data show that it crystallizes as a dimer and that, in contrast to other TTM proteins, it has an open β-barrel structure. We demonstrate that NeuTTM is a highly specific inorganic triphosphatase, hydrolyzing tripolyphosphate (PPPi) with high catalytic efficiency in the presence of Mg2+. These data are supported by native mass spectrometry analysis showing that the enzyme binds PPPi (and Mg-PPPi) with high affinity (Kd < 1.5 μm), whereas it has a low affinity for ATP or thiamine triphosphate. In contrast to Aeromonas and Yersinia CyaB proteins, NeuTTM has no adenylyl cyclase activity, but it shares several properties with other enzymes of the CYTH superfamily, e.g. heat stability, alkaline pH optimum, and inhibition by Ca2+ and Zn2+ ions. We suggest a catalytic mechanism involving a catalytic dyad formed by Lys-52 and Tyr-28. The present data provide the first characterization of a new type of phosphohydrolase (unrelated to pyrophosphatases or exopolyphosphatases), able to hydrolyze inorganic triphosphate with high specificity. |
| Databáze: | OpenAIRE |
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