Strongly increases vascular permeability, and weakly stimulates angiogenesis. Interacts with human VEGF receptor-1 (FLT1) with a high affinity, whereas it binds to human VEGF receptor-2 (KDR) with a low affinity. Stimulates autophosphorylation of VEGF receptor-1 (VEGFR-1/FLT1), and VEGF receptor-2 (VEGFR-2/KDR). Homodimer; disulfide-linked. Interacts with human VEGF receptor-1 (FLT1) with a high affinity, whereas it binds to human VEGF receptor-2 (KDR) with a low affinity. Does not bind VEGF receptor-3 (FLT4). Expressed by the venom gland. IC(50) to VEGF receptor-1 is 30 ng/ml and IC(50) to VEGF receptor-2 is 254 ng/ml. Belongs to the PDGF/VEGF growth factor family. Snake venom VEGF subfamily.