Oocyte fertilization triggers acid phosphatase activity during Rhodnius prolixus embryogenesis

Acid phosphatase activity, previously identified in Rhodnius prolixus oocytes, was studied during egg development. Fertilized eggs exhibited a five fold increase of total acid phosphatase activity during the first days of development. In contrast non-fertilized oviposited eggs showed no activation of this enzyme. An optimum pH of 4.0 for pNPP hydrolysis in a saturable linear reaction and a strong inhibition by lysosomal acid phosphatase inhibitors such as NaF (10 mM) and Na(+)/K(+) tartrate (0.5 mM) are the major biochemical properties of this enzyme. Fractionation of egg homogenates through gel filtration chromatography revealed a single peak of activity with a molecular mass of 94 kDa. The role of this enzyme in VT dephosphorylation was next evaluated. Western blots probed with anti-phosphoserine polyclonal antibody demonstrated that VT phosphoaminoacid content decreases during egg development. In vivo dephosphorylation during egg development was confirmed by following the removal of (32)P from (32)P-VT in metabolically labeled eggs. Vitellin was the only phosphorylated molecule able to inhibit pNPPase activity of partially purified acid phosphatase. These data indicate that acid phosphatase activation follows oocyte fertilization and this enzyme seems to be involved in VT dephosphorylation.