glutamine to glutamate introduces a negative charge, which increases its ability to bind to celiac antibodies, enhancing antigenicity [15]. tTG can even bind gliadin peptides to itself through cross-linking, and this may account for the antibodies to tTG that are characteristic of CD [16]. tTG can also bind undigested gliadin peptides to lysine residues in collagen, and it has been argued that this can explain antibodies to collagen associated with CD [17].
Because uncontrolled activity of tTG can cause dramatic effects on proteins, making them more allergenic and hooking them together in unpredictable ways, the enzyme is kept in check through clever regulatory processes. It is normally kept in an inactive (physically closed) state, and is activated (opened) under appropriate circumstances by calcium binding. The celiac-related antibodies to tTG only respond to the open state of the molecule [15]. Inside the cell, tTG is typically kept in the closed inactive configuration through binding to a molecule called guanosine triphosphate (GTP). tTG also exists extracellularly, where it is normally attached to heparan sulfate, which also keeps it in a closed inactive state, awaiting signaling mechanisms in response to stressors to wake it up.
3 Gliadin and NF-κB
NF-κB (Nuclear Factor kappa-light-chain-enhancer of activated B cells) is a rapid first responder to all kinds of stressors in mammalian cells, including free radicals, heavy metals, ultraviolet irradiation, oxidized LDL, and bacteria and viruses. NF-κB is constitutively active in the intestinal mucosa of patients with untreated CD, and is considered central to intestinal inflammation [18]. NF-κB is normally kept on standby through binding to a protein called IκBα (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha). This protein binds tightly to NF-κB, keeping it in the cytoplasm so that it is unable to migrate to the nucleus and activate an inflammatory response.
A paper published in 2012 explained how gliadin peptides could collaborate with tTG to induce the inflammatory response that is characteristic of CD [19]. In their proposed model, undigested gliadin peptides entering the cells rapidly induce calcium release from the endoplasmic reticulum (ER) and from the mitochondria, an experimentally observed fact. The increase in cytoplasmic calcium levels activates tTG, which will then deamidate gliadin peptides and produce cross links between gliadin and tTG and between gliadin and other cellular proteins. This creates all kinds of immunogenic proteins. In addition, cross links formed in IκBα frees up NF-κB, allowing it to translocate to the nucleus and initiate an inflammatory response.
4 Glyphosate Acting as a Glycine Analogue
I believe that glyphosate has an insidious, cumulative mechanism of toxicity that relates to its role as an analogue of the coding amino acid glycine. Glyphosate is a complete glycine molecule, except that the nitrogen atom has a methylphosphonyl group attached to it in place of a hydrogen atom in glycine. As such, it is possible that glyphosate is able to substitute by mistake for glycine during protein synthesis. There is considerable evidence in support of this hypothesis in the published research literature, as elaborated in several papers that I have published together with colleagues [20, 21, 22]. Perhaps the strongest evidence comes from the research literature on glyphosate’s suppression of 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase in the shikimate pathway in plants. This is believed to be its main mechanism of toxicity in plants.
EPSP synthase binds the phosphate anion in phosphoenolpyruvate (PEP) at a site containing a highly conserved glycine residue, as well as two nearby positively charged (cationic) amino acids that anchor the phosphate anion in place through ionic bonding to the negatively charged phosphate. The enzyme has to configure itself so as to make room for PEP to bind to it. Glyphosate should fit comfortably into the space reserved for the phosphate of PEP, because its extra methylphosphonate unit is very similar to phosphate, both in terms of size, shape and electric charge. It will also be attracted to the site because of the support from the nearby cationic amino acids. But, its bulky methylphosphonate unit will displace the phosphate of PEP and disrupt enzyme function in a major way.