Typically, A2M inhibits the active target proteinase by a trapping mechanism (for a review see: [136]). Functional analysis of the P. monodon A2M revealed that it can bind to syntenin, a cytosolic protein with diverse biological functions [137]. Also, A2M may facilitate the entry of the phagocytosis activating protein (PAP) into phagocytic cells and increase the survival rate of the shrimp after being infected by WSSV [138].