Bromelain is 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. Substrates susceptible to bromelain include all of the common protein materials such as gelatin, casein, gluten, collagen, elastin, globulins an muscle fiber protein. It is a cysteine endopeptidase with broad specificity for cleavage of proteins. It may be from a stem or piece of fruit.

• Readily soluble in water, insoluble in most organic solvents such as acetone, ether, ethanol and methanol
• Enzyme Commission Number: E.C. 3.4.22.4
• Isoelectric point (pI): 9,551

It may be used to inhibit the biosynthesis of proinflammatory prostaglandins. It may be used to reduce clotting efficiency. It is from pineapple stem, has been used to make enzymatic hydrolysates of honeybee-collected pollen.

Activators: Bromelain can be activated by cysteine, bisulphite salt, NaCN, H₂S, Na₂S and benzoate; however, bromelain is usually sufficiently active without the addition of activators. Generally, if bromelain loses an appreciable amount of its activity by undue storage or preparation conditions, the enzyme can be markedly reactivated by cysteine. Inhibitors: Bromelain is inhibited by Hg²⁺, Ag+, Cu²⁺, α-1-antitrypsin, estatin A & B, Iodoacetate, TLCK, TPCK. Preferential Cleavage: Lys-, Ala-, Tyr-, Gly-.

Unit definition: One unit will hydrolyse 1,0 mg of amino nitrogen from gelatin in 20 m at pH 4,5 at 45 °C.