Actinidain

Actinidain was first identified in 1959 when A.C. Arcus examined why jellies made with kiwifruit did not solidify, an effect caused by a proteolytic enzyme acting on gelatin. A thiol group was identified to be essential for enzyme activity, which is why it was grouped with enzymes like papain and bromelain. == Function ==

While no clear function has been identified, the enzyme begins to accumulate in the immature fruit and is suspected to be important for fruit development. Actinidain has a detrimental effect on the larvae of Spodoptera litura, although its use as a pesticide has not been established. == Sequence and structure ==

Actinidain has an enzyme classification number (EC) of 3.4.22.14. The 3 classifies it as a hydrolase. It is further classified as acting on peptide bonds, also known as a peptidase (3.4). The .22 represents the cysteine endopeptidases and then the .14 is actinidain’s unique identifier within that group. Actinidain is active over a wide range of pH, including very acidic conditions, with a pH optimum from 5-7. At least ten different isoforms that all have the same molecular weight and cysteine protease activity as actinidain have been identified but they vary in isoelectric point from acidic (pI 3.9) to basic (pI 9.3). ==Allergic potential ==

Actinidain is the major allergen in kiwifruit, with the reaction presenting as mild symptoms in the mouth. ==Food applications ==

Actinidain is used as a high-quality meat tenderizer. Studies have shown that actinidain might be a good alternative milk coagulant, replacing chymosin, a common coagulant used in cheese making. == References ==