A glycoprotein which is a highly active thiol proteinase (non-specific cysteine protease), which splits glycine esters but not lysine esters; it is also a protein-digesting and milk-clotting enzyme. It is found in the leaves and stems of the pineapple plant. Substrates susceptible to bromelain include all of the common protein materials such as gelatin, casein, gluten, collagen, elastin, globulins an muscle fiber protein.