It is possible to isolate mutant bacteria that are phenylalanine auxotrophs, tha

Question

It is possible to isolate mutant bacteria that are phenylalanine auxotrophs, that is they require phenylalanine in the medium in order to grow: non-mutant bacteria, of course, are able to synthesize their own phenylalanine via the shikimate pathway. A phenylalanine auxotroph (with one mutation in the shikimate pathway) is able to grow well in the presence of phenylalanine, but as soon as the added phenylalanine is used up, these bacteria stop growing and begin to excrete a metabolite of the shikimate pathway. Explain in detail why these bacteria don't begin to excrete this metabolite before using up the phenylalanine in the medium.

Explanation / Answer

Phenylalanine is transformed into norepinephrine in the body through a variety of metabolic steps, as well as to other active chemicals, such as epinephrine, dopamine, and tyramine. Norepinephrine is an important neurotransmitter that conveys information from nerve to nerve and is apparently important for memory, alertness, and learning.

Practitioners recommend phenylalanine for treatment of depression, bipolar disorder, hyperactivity, and Parkinson

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