Aureolysin (EC 3.4.24.29, protease III, staphylococcal metalloprotease, Staphylococcus aureus neutral proteinase) is an extracellular metalloprotease expressed by Staphylococcus aureus.[1][2][3][4][5] This protease is a major contributor to the bacterium's virulence, or ability to cause disease, by cleaving host factors of the innate immune system as well as regulating S. aureus secreted toxins and cell wall proteins.[6][7] To catalyze its enzymatic activities, aureolysin requires zinc and calcium which it obtains from the extracellular environment within the host.[6][7]