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A Mitochondrial Membrane Exopolyphosphatase Is Modulated by, and Plays a Role in, the Energy Metabolism of Hard Tick Rhipicephalus (Boophilus) microplus Embryos
Laboratório Integrado de Bioquímica—Hatisaburo Masuda, UFRJ, Polo Barreto, Rua Rotary Club s/n, São José do Barreto, Macaé, RJ, C.P. 119.331, CEP 27971–220, Brazil
Instituto Nacional de Ciência e Tecnologia—Entomologia Molecular, Rio de Janeiro, RJ, CEP 21941–590, Brazil
Laboratório de Química e Função de Proteínas e Peptídeos, Laboratório de Biologia Celular e Tecidual and Unidade de Experimentação Animal–CBB–UENF, Avenida Alberto Lamego, 2000, Horto, Campos dos Goytacazes, RJ, CEP 28015–620, Brazil
Centro de Biotecnologia e Faculdade de Veterinária, UFRGS, Avenida Bento Gonçalves, 9090, Porto Alegre, RS, C.P. 15005, CEP 91501–970, Brazil
Centro de Biotecnologia, UFRGS, Avenida Bento Gonçalves, 9500, prédio 43421, Porto Alegre, RS, C.P. 15005, CEP 91501–970, Brazil
* Author to whom correspondence should be addressed.
Received: 22 April 2011; in revised form: 14 May 2011 / Accepted: 19 May 2011 / Published: 3 June 2011
Abstract: The physiological roles of polyphosphates (polyP) recently found in arthropod mitochondria remain obscure. Here, the relationship between the mitochondrial membrane exopolyphosphatase (PPX) and the energy metabolism of hard tick Rhipicephalus microplus embryos are investigated. Mitochondrial respiration was activated by adenosine diphosphate using polyP as the only source of inorganic phosphate (Pi) and this activation was much greater using polyP3 than polyP15. After mitochondrial subfractionation, most of the PPX activity was recovered in the membrane fraction and its kinetic analysis revealed that the affinity for polyP3 was 10 times stronger than that for polyP15. Membrane PPX activity was also increased in the presence of the respiratory substrate pyruvic acid and after addition of the protonophore carbonyl cyanide-p-trifluoromethoxyphenylhydrazone. Furthermore, these stimulatory effects disappeared upon addition of the cytochrome oxidase inhibitor potassium cyanide and the activity was completely inhibited by 20 µg/mL heparin. The activity was either increased or decreased by 50% upon addition of dithiothreitol or hydrogen peroxide, respectively, suggesting redox regulation. These results indicate a PPX activity that is regulated during mitochondrial respiration and that plays a role in adenosine-5’-triphosphate synthesis in hard tick embryos.
Keywords: inorganic polyphosphate; respiration; membrane exopolyphosphatase; arthropod; energy metabolism
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Campos, E.; Façanha, A.R.; Costa, E.P.; Fraga, A.; Moraes, J.; Da Silva Vaz Jr., I.; Masuda, A.; Logullo, C. A Mitochondrial Membrane Exopolyphosphatase Is Modulated by, and Plays a Role in, the Energy Metabolism of Hard Tick Rhipicephalus (Boophilus) microplus Embryos. Int. J. Mol. Sci. 2011, 12, 3525-3535.
Campos E, Façanha AR, Costa EP, Fraga A, Moraes J, Da Silva Vaz Jr. I, Masuda A, Logullo C. A Mitochondrial Membrane Exopolyphosphatase Is Modulated by, and Plays a Role in, the Energy Metabolism of Hard Tick Rhipicephalus (Boophilus) microplus Embryos. International Journal of Molecular Sciences. 2011; 12(6):3525-3535.
Campos, Eldo; Façanha, Arnoldo R.; Costa, Evenilton P.; Fraga, Amanda; Moraes, Jorge; Da Silva Vaz Jr., Itabajara; Masuda, Aoi; Logullo, Carlos. 2011. "A Mitochondrial Membrane Exopolyphosphatase Is Modulated by, and Plays a Role in, the Energy Metabolism of Hard Tick Rhipicephalus (Boophilus) microplus Embryos." Int. J. Mol. Sci. 12, no. 6: 3525-3535.