Reference
Protease Inhibitor (Potato)
**Protease Inhibitor (Potato)** is a family of small proteins in the potato tuber that block the activity of protease (protein-digesting) enzymes; together with patatin, protease inhibitors form the two major protein fractions found in potato protein isolate.
Types and structure
Potato protease inhibitors are not a single molecule but a heterogeneous group, typically classified by which enzyme family they target. Two well-studied classes are the Kunitz-type inhibitors and the Bowman-Birk inhibitors (BBIs). Bowman-Birk inhibitors primarily inhibit serine peptidases of the S1 family. A specific potato Kunitz-type inhibitor has been identified and named PKPI-9.0. The proteinase inhibitor PI2 also occurs naturally in potatoes.
These proteins are comparatively small, which contributes to the lower average molecular weight of the protease-inhibitor fraction relative to patatin, the larger glycoprotein fraction.
Functional and biological roles
In the living plant, protease inhibitors serve a defensive function: potato PKPI and Pin1 inhibitors are associated with insecticidal and nematicidal activity (Frontiers in Plant Science, 2020, PMID:32425963). In food systems they retain enzyme-blocking behaviour — potato protein isolate has shown functional value as a protease inhibitor and gel enhancer in a surimi matrix (PMID:36230190), and potato-derived trypsin inhibitors have been studied for their effect on the gel properties of chicken mince (PMID:40645055).
Protease inhibitors are also examined for human-health relevance. Potato proteins contain protease inhibitors that may help prevent protease-induced peri-anal dermatitis (European Journal of Clinical Investigation, 2004, PMID:15086363), and the potato is described as a source of protease inhibitors in a review of their broader activity (International Journal of Molecular Sciences, 2009, PMID:19582234). Plant protease inhibitors have also been investigated for antiviral potential, including against SARS-CoV-2 (Journal of Infectious Diseases and Treatment, 2021).
Satiety and digestion — what the evidence supports
The protease-inhibitor fraction is often mentioned in connection with appetite, since PI2 has been linked to a trypsin-dependent cholecystokinin (CCK) mechanism. However, the evidence is limited: reviews of plant protease inhibitors as pharmacological targets emphasize inflammation, coagulation, and cancer, and do not highlight satiety or CCK as established areas. Trypsin inhibitors are also classed as anti-nutrients, meaning they can interfere with protein digestion. Claims beyond what these studies show are not warranted.
Relevance to potato protein and allergens
Protease inhibitors matter to anyone reading a label, because the primary potato allergens are patatin (Sol t 1) and several protease inhibitors (Sol t 2, Sol t 3, Sol t 4). Cross-reactivity among Solanaceae members (potato, tomato, pepper, eggplant) is possible but not universal, owing partly to homologous patatin-like and protease-inhibitor proteins (Case Reports in Pediatrics, 2025, PMID:40955319). For a fuller overview of how these fractions fit together, see what potato protein is.
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