Dopamine production by gut bacteria and its role in the progression of Parkinson\u27s disease

Gut dysbiosis is a well documented pre-motor symptom of Parkinson’s disease (PD). Various populations of bacteria are found to be out of balance in the guts of PD patients across the world. Among these bacteria are genera with the potential to produce dopamine, a neurotransmitter with a critical role in PD. Sequence analysis was used to compare the genomes of bacteria exhibiting dysbiosis in PD patients, and the sequences of key enzymes in the dopamine biosynthetic pathway, including tyrosine hydroxylase, as well as tyrosine decarboxylase or DOPA decarboxylase. Alternatives to these enzymes were also investigated. The genera Bacteroides and Clostridium were identified as having sequence similarity with tyrosine hydroxylase, tyrosine or DOPA decarboxylase, as well as a tetrahydrobiopterin synthesis enzyme. Although further studies will be necessary to demonstrate that these bacteria have the ability to produce dopamine, and that they can do so while residing in the gastrointestinal tract, this work has laid the foundation for future research on the role of the gut microbiota in PD