Tryptophan oxygenase

Brett PM, Curtis D, Robertson MM, Curling HM (1995) Exclusion of the 5-HTlA serotonin neuroreceptor and tryptophan oxygenase genes in a large British kindred multiply affected with Tourette s syndrome, chronic motor tics, and obsessive-compulsive behavior. Am J Psychiatry 152 437-440... 

Cyclins Proteinkinase A Tryptophan oxygenase y-Glutamyl transferase... 

Limited data suggest that tryptophan oxygenase activity subject to similar structural criteria as catalase activity, but adrenaline and other phenols also active... 

Tryptophan oxygenase is another iron-containing enzyme which, like catalase, is inhibited by pyrazole in vivo but not in vitro. Again, however, the metabolite 4-hydroxypyrazole is active in vitro and shows, in contrast to catalase, competitive inhibition with tryptophan for the enzyme (79MI10505). Adrenaline and other phenols are also inhibitors of this enzyme and in this case, therefore, the heterocyclic ring appears not to be essential for activity. 

Bischler-Napieralski reactions, 4, 279 carboline synthesis from, 4, 516 Mannich-type reactions, 4, 279 sulfur isosteres, biological activity, 4, 913 synthesis, 4, 337, 913 Tryptophan biosynthesis, 1, 264 carboline synthesis from, 4, 516 molecular structure, 4, 162 Tryptophan hydroxylase in serotonin biosynthesis, 1, 261 Tryptophan oxygenase... 

For additional members of the late fetal (A), neonatal (B), and late suckling (C) cluster of enzymes see ref. 8. G6P-ase, glucose-6-phosphatase glutamate DH, glutamate dehydrogenase malate-NADP DH, malic enzyme TRY Oxygenase, tryptophan oxygenase. 

GH has been shown to induce a number of enzymes concerned with amino acid metabolism in the liver of the hypophysectomized rat (in vivo or in perfused liver [78]). Induced enzymes include tyrosine aminotransferase, tryptophan oxygenase and ornithine decarboxylase. The effects are complex, particularly in relation to interaction with glucocorticoids, and in some experiments GH lowered enzyme levels induced by glucocorticoids, although given alone it led to induction of these enzymes. 

The first enzyme of the pathway, tryptophan dioxygenase (also known as tryptophan oxygenase or tryptophanpyrrolase), is rate-limiting under normal conditions. In isolated hepatocytes, the control coefficient for flux through the pathway of tryptophan dioxygenase is 0.75 and that for tryptophan uptake into the cells is 0.25 (Salter et al., 1986). 

Besansky, N. J., Mukabayire, O., Benedict, M. Q., Rafferty, C. S., Hamm, D. M., and McNitt, L., The Anopheles gambiae tryptophan oxygenase gene expressed from a baculovirus promoter complements Drosophilia melanogaster vermilion, Insect Biochem. Mol. Biol, T7, 803, 1997. 

Merkulov, V. M. and Merkulova, T. I., Nucleotide sequence of a fragment of the rat tryptophan oxygenase gene showing high affinity to glucocorticoid receptor in vitro, Biochim. Biophys. Acta, 1132, 100, 1992. 

Kaltschmidt, C., Muller, M., Brem, G., and Renkawitz, R., DNAse I hypersensitive sites far upstream of the rat tryptophan oxygenase gene direct develop-mentally regulated transcription in livers of transgenic mice, Mech. Dev., 45, 203, 1994. 

Chikhirzhina, G. I., Romanovskaia, E. V., Nazarova, N. Iu., and Fedorova, S. A., Interaction of the regulatory region of the tryptophan oxygenase gene with transcription factors of the nuclear factor 1 (NF 1) family, Tsitologiia, 41, 939, 1999. 

Comings, D. E., Muhleman, D., Dietz, G. W., Jr., and Donlon, T., Human tryptophan oxygenase localized to 4q31 Possible implications for alcoholism and other behavioral disorders, Genomics, 9, 301, 1991. 

Plasma tryptophan concentration is a function of dietary tryptophan intake as well as the extent of removal of tryptophan from blood by tissues. The liver is the main organ influencing plasma tryptophan concentration since it actively metabolizes tryptophan while nonhepatic tissues have only relatively limited ability to act in this manner. Following a meal, in the liver, tryptophan stimulates hepatic tryptophan oxygenase activity, which affects tryptophan catabolism and determines how much tryptophan enters the general circulation. 

A decrease in circulating tryptophan levels may be of importance in some models of hypertension. The DS rat is an example of this. The reduction in plasma tryptophan was clearly associated with the excess intake of NaCl and concomitant elevation in blood pressure. Mechanisms that could account for the reduction in plasma tryptophan could include a decrease in gastrointestinal absorption of tryptophan, an increase in urinary tryptophan excretion, increased oxidation of tryptophan by tryptophan oxygenase, and aberrant regulation (hormonal, nutrient, plasma protein) of tryptophan... 

Stowell, L. and Morland, J., Ethanol-induced increase in liver tryptophan oxygenase activity in the starved rat Evidence against tryptophan mediation, Biochem. Pharmacol., 33, 2397, 1984. 

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