Porphyromonas gingivalis produces gingipains that degrade tau protein, potentially leading to Alzheimer's tangles.

“The mechanism is specific. P. gingivalis produces enzymes called gingipains. Two types: one cuts proteins at lysine residues, the other at arginine. Tau, the protein that holds your neuronal scaffolding together, is loaded with both amino acids. In cell culture, gingipains shred soluble tau within one hour of infection. The fragments seed the paired helical filaments that become tangles. Tangles are Alzheimer's.”