Bacterial Metabolism, Neurotransmitters, Migraine Headaches, and Birth Defects
Some of these substances mimic neurotransmitters, others affect (dilation of) blood vessels. Looking up these molecules, tyramine is indeed similar in shape to DOPA, dopamine, norepinephrine, and epinephrine. And the resemblance is more than coincidental; these neurotransmitters and tyramine are all derived from tyrosine (which is derived from the amino acid phenylalanine).
These compounds are also produced by fermentation and putrefaction, hence the caution about fermented foods. So why would important signaling molecules in eukaryotes be so similar to bacterial byproducts? Wouldn't this make these organisms terribly vulnerable to the presence of bacteria?
The reason lies in the origins of relationships between eukaryotes and bacteria. Membranes, in addition to containing cytoplasm, facilitate the maintenance of reactant gradients. Because the feedstocks for bacterial metabolism and the waste products must ultimately be outside of the cell, the plasma membrane is an integral part of vital chemical processes. These waste products also control the metabolic activity of the other species in bacterial communitites.
Detecting these waste products became the method of sensing the presence and direction of bacteria for the first highly mobile protozoans (eukaryotes). Sensing, locomotion, and digestion are tightly coupled activities for predators even now.
When bacteria were absorbed into eukaryotes as organelles, this signaling served to coordinate operation and reproduction of the organelles; just as it had in free bacterial communities. Prokaryotes (bacteria and archea) are the experts in chemistry; eukaryotes excel in controlling and combining their activities.
So the signal molecules for sensing, locomotion, and digestion are inherited from the bacterial processes of an ancient age.
But the need to produce, diffuse and dispose of signal molecules is key to the configuring of tissues. Protozoans had genes for these processes for many signals. The natural solution was to employ the less commonly used signals for morphogenesis. The intricate controls at which eukaryotes excel were easier for eukaryotes to develop than new, unique markers.
In light of this overloading of functions on signal molecules, it is clear that the presence of those molecules during particular periods of fetal development will result in fetal deformities or death.
The next chapter is Viruses and Bacteria -- Flagellum
Copyright © 2003 Aubrey Jaffer
I am a guest and not a member of the MIT Computer Science and Artificial Intelligence Laboratory.
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