Cysteine protease

Large group of enzymes (9 clans with about 60 families) belonging to the hydrolases and their subgroup of proteases or peptidases. The enzyme papain belongs to the cysteine proteases, as do caspases. They are characterised by a catalytic degradation of a peptide to the amino acids cysteine and histidine. Of allergological significance is actinidine, a cysteine protease of the kiwi fruit (Act d 1), a marker allergen for primary kiwi sensitization. Actinidine is used in the food industry as a meat softener. Actinidine also breaks down proteins in dairy products, so kiwi extracts should not be mixed with milk.

1. Dearman RJ et al (2014) Characterization of the allergenic potential of proteins: an assessment of the kiwifruit allergenic actinidin. J Appl Toxicol 34:489-497.
2. Grozdanovic MM et al (2016) Kiwifruit cysteine protease actinidin compromises the intestinal barrier by disrupting tight junctions. Biochim Biophys Acta 1860:516-526.