Inorganic polyphosphates regulate hexokinase activity and reactive oxygen species generation in mitochondria of
Amanda Fraga1, Jorge Moraes, José Roberto da Silva
1Laboratório 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.
Abstract:
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.
Insights
Polyphosphates (poly P) in tick mitochondria influence reactive oxygen species. Inorganic polyphosphate and exopolyphosphatase regulate mitochondrial reactive oxygen species generation in Rhipicephalus microplus embryos.
Area of Science:
- Mitochondrial biochemistry
- Tick embryogenesis
- Reactive oxygen species metabolism
Background:
- The physiological functions of polyphosphates (poly P) in arthropod mitochondria are not well understood.
- Poly P has been recently identified in arthropod mitochondria, prompting investigation into its roles.
- Mitochondria are key organelles involved in cellular respiration and reactive oxygen species (ROS) production.
Purpose of the Study:
- To investigate the role of polyphosphates (poly P) in reactive oxygen species (ROS) generation within the mitochondria of Rhipicephalus microplus embryos.
- To examine the influence of poly P on mitochondrial hexokinase and scavenger antioxidant enzymes during embryogenesis.
- To elucidate the relationship between poly P, exopolyphosphatase activity, and ROS production in tick mitochondria.
Main Methods:
- Assaying mitochondrial hexokinase and scavenger antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase) during Rhipicephalus microplus embryogenesis.
- Analyzing the effects of poly P₃ and poly P₁₅ on enzymatic activities during periods of high metabolic activity.
- Measuring hydrogen peroxide generation in mitochondria under varying conditions of poly P and hexokinase activity.
Main Results:
- Both poly P₃ and poly P₁₅ significantly inhibited hexokinase activity (up to 90%).
- Mitochondrial membrane exopolyphosphatase activity was stimulated by glucose-6-phosphate, a product of hexokinase.
- Poly P enhanced hydrogen peroxide generation in active mitochondria, indicating a role in ROS production.
- Antioxidant enzyme activities varied during embryogenesis and showed differential responses to poly P₃ and poly P₁₅, with glutathione reductase being consistently stimulated.
Conclusions:
- Inorganic polyphosphate (poly P) and mitochondrial membrane exopolyphosphatase are potentially involved in regulating reactive oxygen species (ROS) generation in Rhipicephalus microplus embryos.
- Poly P influences key enzymes in mitochondrial metabolism and antioxidant defense pathways.
- The findings suggest a complex interplay between poly P, energy metabolism, and oxidative stress in tick development.
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