1. Laboratório Integrado de Bioquímica—Hatisaburo Masuda, UFRJ, Polo Barreto, Av. São José do Barreto nº 764, São Jose do Barreto, CEP 27971-550, Macaé, RJ, Brazil;
2. Instituto Nacional de Ciência e Tecnologia—Entomologia Molecular, Rio de Janeiro, RJ, CEP 21941-590, Brazil;
3. Laboratório de Química e Função de Proteínas e Peptídeos and Unidade de Experimentação Animal-CBB-UENF, Avenida Alberto Lamego, 2000, Horto, Campos dos Goytacazes, RJ, CEP 28015-620, Brazil;
4. Centro de Biotecnologia e Faculdade de Veterinária, UFRGS, Avenida Bento Gonçalves, 9090, Porto Alegre, RS, C.P. 15005, CEP 91501-970, Brazil.
The physiological roles of polyphosphates (poly P) recently found in arthropod mitochondria remain obscure. Here, the possible involvement of poly P with reactive oxygen species generation in mitochondria of Rhipicephalus microplus embryos was investigated. Mitochondrial hexokinase and scavenger antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione reductase were assayed during embryogenesis of R. microplus. The influence of poly P3 and poly P15 were analyzed during the period of higher enzymatic activity during embryogenesis. Both poly Ps inhibited hexokinase activity by up to 90% and, interestingly, the mitochondrial membrane exopolyphosphatase activity was stimulated by the hexokinase reaction product, glucose-6-phosphate. Poly P increased hydrogen peroxide generation in mitochondria in a situation where mitochondrial hexokinase is also active. The superoxide dismutase, catalase and glutathione reductase activities were higher during embryo cellularization, at the end of embryogenesis and during embryo segmentation, respectively. All of the enzymes were stimulated by poly P3. However, superoxide dismutase was not affected by poly P15, catalase activity was stimulated only at high concentrations and glutathione reductase was the only enzyme that was stimulated in the same way by both poly Ps. Altogether, our results indicate that inorganic polyphosphate and mitochondrial membrane exopolyphosphatase regulation can be correlated with the generation of reactive oxygen species in the mitochondria of R. microplus embryos.
Keywords: inorganic polyphosphate, reactive oxygen species, arthropod, mitochondria, scavenger antioxidant enzymes.