Abstract
The ability of 5-HT neurons to regulate 5-HT synthesis under different degrees of neuronal activity apparently resides in the initial, rate-limiting step in 5-HT formation, the hydroxylation of tryptophan to 5-hydroxtryptophan (5-HT) by tryptophan hydroxylase (Herr et al., 1975). One mechanism for producing rapid alterations in 5-HT synthesis of this kind, that seems likely to have a significant role in the short term regulation of 5-HT synthesis, is modulation of the kinetic behaviour of the tryptophan hydroxylase molecule. A great deal of evidence indicates that the kinetic properties of this enzyme can be altered in soluble preparations by a variety of agents including some that are known to be physiological regulators e.g. ATP, magnesium and calcium (Hamon, et al., 1978; Kuhn, et al., 1978). However, the evidence that the kinetic behaviour of tryptophan hydroxylase is actually regulated in vivo in response to nerve impulse flow remains largely indirect. The reason for this is that attempts to demonstrate an increase in tryptophan hydroxylase activity in vitro after in vivo stimulation have either been unsuccessful or have met with only limited success.
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Boadle-Biber, M.C. (1981). Regulation of tryptophan hydroxylase activity: studies with slices of rat brain stem and some in vivo treatments. In: Usdin, E., Weiner, N., Youdim, M.B.H. (eds) Function and Regulation of Monoamine Enzymes: Basic and Clinical Aspects. Palgrave Macmillan, London. https://doi.org/10.1007/978-1-349-06276-8_21
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DOI: https://doi.org/10.1007/978-1-349-06276-8_21
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