Toxoplasma gondii is an obligate intracellular parasite that infects all warm-blooded animals and chronically persists in one-third of world's human population. Two invasive life stages of this apicomplexan parasite are found in intermediate hosts: a fast replicating tachyzoite, responsible for acute infection that is rapidly controlled by the immune system and a cyst-forming, slow growing bradyzoite that persists during the entire life span of the host. Both stages presumably export effector proteins to hijack host cellular functions, enabling the acquisition of nutrients and evasion of the host cellular and immune defenses. My project was directed toward the functional dissection of the aspartic protease 5 (TgASP5) contribution to the cleavage and export of effector proteins. An in depth analysis of the knock-out of TgASP5 revealed its essential role for the export of dense granules proteins (GRAs) and for the cleavage of those that harbor a TEXEL (Toxoplasma EXport ELement) motif.