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(6 R )‐Tetrahydrobiopterin Increases the Activity of Tryptophan Hydroxylase in Rat Raphe Slices
Author(s) -
Sawada Makoto,
Sugimoto Takashi,
Matsuura Sadao,
Nagatsu Toshiharu
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb00792.x
Subject(s) - tryptophan hydroxylase , tetrahydrobiopterin , phenylalanine hydroxylase , tryptophan , tyrosine hydroxylase , chemistry , aromatic l amino acid decarboxylase , in vivo , serotonin , endocrinology , medicine , enzyme , cofactor , amino acid , phenylalanine , biochemistry , biology , serotonergic , receptor , microbiology and biotechnology
The effects of (6 R )‐ and (6 S )‐tetrahydrobiopterin (BPH 4 ), tetrahydroneopterin, and 6‐methyltetrahydropterin on the activity of tryptophan hydroxylase were investigated in rat raphe slices. The activity of tryptophan hydroxylase was estimated by measurement of 5‐hydroxytryptophan (5‐HTP) formation under inhibition of aromatic L‐amino acid decarboxylase with use of HPLC‐fluorometric detection. (6 R )‐BPH 4 (the naturally occurring form) at 42 μ M , tetrahydroneopterin at 50 μ M , and 6‐methyltetrahydropterin at 100 μ M increased tryptophan hydroxylase activity to 350, 145, and 146% of control values, respectively. (6 S )‐BPH 4 , however, had no significant effects on tryptophan hydroxylase activity. These results suggest that tryptophan hydroxylase is subsaturating in vivo for the naturally occurring cofactor, (6 R )‐BPH 4 , and that the concentration of (6 R )‐BPH 4 may play an important role for the regulation of tryptophan hydroxylase activity in vivo.