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Issue 9, 2017
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Kiwifruit actinidin digests salivary amylase but not gastric lipase

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Kiwifruit contains the cysteine proteinase actinidin whose strong activity allows kiwifruit to be used as a meat tenderiser. This raises the possibility digestive enzymes, also proteins, are themselves susceptible to degradation by actinidin. Salivary amylase and gastric lipase are exposed to the highest concentrations of actinidin whereas duodenal enzymes are less likely to be inactivated by actinidin due to dilution and inactivation of actinidin by gastric juice. The saliva of six volunteers was exposed to Actinidia deliciosa homogenate and then examined for loss of the starch digesting enzyme, alpha-amylase. In agreement with the known distribution of salivary amylase concentration in saliva, the range of amylase activity within the group of volunteers varied by around 100 fold. Within 5 minutes of incubation of 3 parts saliva to one part green kiwifruit at 37 °C, approximately 85% of the amylase activity was lost. The use of E-64, a selective inhibitor of cysteine proteinases, confirmed that the loss of amylase function was due to actinidin. Amylase protein degradation was followed by SDS-PAGE and western blotting. Recombinant human gastric lipase resisted digestion with kiwifruit even after 30 minutes incubation and remained functionally active after this time period. However, both mountain papaya and pineapple extracts degraded gastric lipase fully during a 30 minutes digestion period. Under conditions where cooked starch is consumed along with kiwifruit it is possible that starch digestion may be retarded whereas lipid digestion in the stomach is unlikely to be affected by kiwifruit consumption.

Graphical abstract: Kiwifruit actinidin digests salivary amylase but not gastric lipase

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Publication details

The article was received on 21 Jun 2017, accepted on 19 Aug 2017 and first published on 22 Aug 2017

Article type: Paper
DOI: 10.1039/C7FO00914C
Citation: Food Funct., 2017,8, 3339-3345
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    Kiwifruit actinidin digests salivary amylase but not gastric lipase

    H. Martin, S. B. Cordiner and T. K. McGhie, Food Funct., 2017, 8, 3339
    DOI: 10.1039/C7FO00914C

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