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Published on: January 7, 2013
A mitochondrial exopolyphosphatase activity modulated by phosphate demand in Rhipicephalus (Boophilus) microplus
Eldo Campos1, Arnoldo Façanha, Jorge Moraes
1Laboratório de Química e Função de Proteínas e Peptídeos and Laboratório de Biologia Celular e Tecidual-CBB-UENF, Avenida Alberto Lamego 2000, Horto, CEP 28015-620 Campos dos Goytacazes, RJ, Brazil.
Abstract:
This study describes Exopolyphosphatases (PPX) activity in mitochondria of Rhipicephalus microplus embryos. Mitochondria were isolated by differential centrifugation and PPX activity was analyzed through the hydrolysis of the substrate Polyphosphate (Poly P(15)). We investigated the influence of NADH, NAD+, Pi and ADP in a concentration range of 0.1-2.0 mM. Poly P hydrolysis was stimulated about two-fold by NADH and strongly inhibited by Pi. The PPX activity also increased in the presence of the respiratory substrates pyruvic and succinic acids, and this stimulatory effect disappeared upon addition of KCN. Mitochondrial respiration was activated by ADP using poly P as the only source of Pi. Endogenous poly P content changed following PPX activity during embryogenesis from the first up to 18th day of development. The data describe exopoly P as being modulated by Pi demand and related to energy supply during embryogenesis of hard ticks.
Insights
Mitochondrial exopolyphosphatase (PPX) activity in Rhipicephalus microplus embryos is influenced by energy supply and phosphate demand. This enzyme plays a role in tick embryogenesis, modulating polyphosphate levels during development.
Area of Science:
- Biochemistry
- Molecular Biology
- Parasitology
Background:
- Exopolyphosphatases (PPX) are enzymes involved in the hydrolysis of polyphosphates.
- Mitochondria are crucial for cellular energy production.
- Rhipicephalus microplus is a significant hard tick species affecting livestock.
Purpose of the Study:
- To characterize exopolyphosphatase (PPX) activity in mitochondria of Rhipicephalus microplus embryos.
- To investigate the regulatory factors influencing PPX activity, including energy substrates and phosphate.
- To understand the role of PPX in polyphosphate metabolism during tick embryogenesis.
Main Methods:
- Isolation of mitochondria from Rhipicephalus microplus embryos via differential centrifugation.
- Assay of PPX activity by measuring the hydrolysis of Polyphosphate (Poly P(15)).
- Evaluation of the effects of NADH, NAD+, Pi, ADP, pyruvic acid, succinic acid, and KCN on PPX activity and mitochondrial respiration.
Main Results:
- NADH approximately doubled Poly P hydrolysis, while inorganic phosphate (Pi) strongly inhibited it.
- PPX activity increased with respiratory substrates (pyruvic and succinic acids), an effect abolished by KCN.
- Mitochondrial respiration was activated by ADP when poly P was the sole Pi source.
- Endogenous poly P content varied during embryogenesis, correlating with PPX activity.
Conclusions:
- Mitochondrial exopolyphosphatase activity in Rhipicephalus microplus embryos is modulated by inorganic phosphate demand.
- PPX activity is linked to cellular energy supply during tick embryogenesis.
- Polyphosphate metabolism regulated by PPX is integral to the developmental processes in hard ticks.
