The hard tick Boophilus microplus is responsible for great economical losses. It is an ectoparasite of bovine herd, and a vector for several disease agents. Boophilus microplus is a one-host tick that causes major losses to bovine herds, especially in tropical regions, and major efforts have been made to develop immunoprophylatic tools against it. In this sense, knowledge of the processes involved in embryonic development may unravel additional targets that could be effective in the control of this ectoparasite.
          Linear polyphosphates are energy–rich polymers of up to several hundreds of orthophosphate residues. The biological function of polyps is uncertain and may be different in different organisms or compartments within the same cell and regulating many biochemical processes. One of the enzymes participating in polyp metabolism is exopolyphosphatase.  This enzyme releases orthophosphate from the end of the polyP polymers chain.The exopolyP activity of nuclei and mitochondria were examined using preparation of corresponding subcellular fractions isolated from the B. microplus eggs.
          The purity and intactness of nuclear fraction was rather satisfactory as determined by examination in the phase-contrast microscope. The nuclear purity was also characterized biochemically by absence of marker enzymes of other compartments. In isolated nuclei no activity of ATPase azide sensitive, a marker enzyme of mitochondria, or glucose-6-phosphate dehydrogenase, a marker of cytosol, could be detected. In isolated mitochondria was detected ATPase azide sensitive activity.  In mitochondria the activity was higher during cellularization and in nuclei was higher during the end of embryogenesis. In the presence of 2.5 mM Mg⁺², apparent Km values with polyP₃ as substrate were 0.7 mM and 0.28 mM and with polyP₁₂ were 1.1 mM and 2.8 mM for nuclei and mitochondria respectively. The apparent Ki values using heparin as inhibitor with polyP₁₂ as substrate were 0.1 µg/mL and 0.5 µg/mL for nuclei and mitochondria respectively. Analysis of chain lengths of the polyphosphates during embryogenesis was performed by gel electrophoresis on a 16.5 % polyacrylamide/7M urea gel.
          The obtained results will help us to better understand the polyphosphate metabolism during the B. microplus embryogenesis.
           Supported by PRONEX, FAPERJ, CNPq and CAPES.