Typically, A2M inhibits the active target proteinase by a trapping mechanism . Functional analysis of the P. monodon A2M revealed that it can bind to syntenin, a cytosolic protein with diverse biological functions . 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.