Streptopain (EC 3.4.22.10, Streptococcus peptidase A, streptococcal cysteine proteinase, Streptococcus protease) is an enzyme. This enzyme catalyses the following chemical reaction Streptopain (EC 3.4.22.10, Streptococcus peptidase A, streptococcal cysteine proteinase, Streptococcus protease) is an enzyme. This enzyme catalyses the following chemical reaction This enzyme is isolated from the bacterium, group A Streptococcus.