NPP-BJ, a nucleotide pyrophosphatase/phosphodiesterase from Bothrops jararaca snake venom, inhibits platelet...

Enzymes of the pyrophosphatase/phosphodiesterase family have multiple roles in extracellular nucleotide metabolism and in the regulation of nucleotide-based intercellular signaling. Snake venoms contain enzymes that hydrolyze nucleic acids and nucleotides, but their function is poorly understood. Here we describe for the first time the isolation and functional characterization of a soluble phosphodiesterase from Bothrops jararaca venom, which shows amino acid sequence similarity to mammalian nucleotide pyrophosphatase/phosphodiesterase 3 (NPP3), and inhibits ADP-induced platelet aggregation. The enzyme, named NPP-BJ, showed an apparent molecular mass of 228 kDa by size exclusion chromatography. NPP-BJ exhibited nuclease activity as well as pyrophosphatase and phosphatase activities, preferentially hydrolyzing nucleoside 5'-triphosphates over nucleoside 5'-diphosphates, but was not active upon nucleoside 5'-monophosphates. Depending on the substrate used, dithiothreitol and EDTA differently inhibited the catalytic activity of NPP-BJ. Platelet aggregation induced by ADP was also abrogated by NPP-BJ, whereas thrombin-induced platelet aggregation was only slightly attenuated. However, polyclonal antibodies raised against NPP-BJ could not abolish the lethal activity of B. jararaca venom. Altogether, these results show that NPP-BJ has a minor contribution to the lethal activity of this venom, but interferes with mechanisms of ADP-induced platelet aggregation.