Viperid snakes show the most complex snake-venom proteomes and offer an intriguing challenge in terms of understanding the nature of their components and the pathological outcomes of envenomation characterized by local and systemic effects. In this work, the venom complexity of eight Bothrops species was analyzed by 2-DE, and their subproteomes of proteinases were explored by 2-D immunostaining and 2-D gelatin zymography, demonstrating the diversity of their profiles. Heparin, a highly sulfated glycosaminoglycan released from mast cells, is involved in anti-coagulant and anti-inflammatory processes. Here, we explored the hypothesis that heparin released upon envenomation could interact with toxins and interfere with venom pathogenesis. We first identified the Bothrops venom subproteome of toxins that bind with high-affinity for heparin as composed of mainly serine proteinases and C-type lectins. Next, we explored the Bothrops jararaca toxins that bind to heparin under physiological conditions and identified a relationship between the subproteomes of proteinases, and that of heparin-binding toxins. Only the non-bound fraction, composed mainly of metalloproteinases, showed lethal and hemorrhagic activities, whereas the heparin-bound fraction contained mainly serine proteinases associated with coagulant and fibrinogenolytic activities. These data suggest that heparin binding to B. jararaca venom components in vivo has a minor protective effect to venom toxicity.2030-01-01