Cysteine Protease

https://en.m.wikipedia.org/wiki/Cysteine_protease

Cysteine proteases are commonly encountered in fruits including papaya, pineapple, fig and kiwifruit.

Papain

https://en.m.wikipedia.org/wiki/Papain

https://en.m.wikipedia.org/wiki/Papain-like_protease

Papain-like Protease

The human genome encodes eleven cysteine cathepsins which have a broad range of physiological functions. In some parasites papain-like proteases have roles in host invasion, such as cruzipain from Trypanosoma cruzi.

In cellular organisms they are synthesized as preproenzymes that are not enzymatically active until mature, and their activities are tightly regulated, often by the presence of endogenous protease inhibitors such as cystatins.

In many RNA viruses, including significant human pathogens such as the coronaviruses SARS-CoV and SARS-CoV-2, papain-like protease protein domains often have roles in processing of polyproteins into mature viral nonstructural proteins. Many papain-like proteases are considered potential drug targets.

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Glycine Cysteine
Protease Glutathione
Adenosine Triphosphate

Prion likely disrupts or hyjack these important chemical reactions.

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Histamine Nitrogen

Histamine is broken down on a regular basis by two enzymes: DAO and HNMT.

Nitrogen N (tau)-methylation

Histamine N-Methyltransferase (HNMT, HMT)

Diamine Oxidase (DAO)

S-Adenosylmethionine (SAM-e)