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PROPERTIES AND REGIONAL DISTRIBUTION OF TRYPTOPHAN HYDROXYLASE IN THE CHICKEN BRAIN
Author(s) -
Mclennan I. S.,
Lees G. J.
Publication year - 1978
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.1471-4159.1978.tb06547.x
Subject(s) - tryptophan hydroxylase , brainstem , midbrain , tryptophan , cerebellum , thalamus , biology , endocrinology , medicine , chemistry , cerebral cortex , biochemistry , central nervous system , neuroscience , serotonin , amino acid , receptor , serotonergic
— Tryptophan hydroxylase in young chicken brain had a pH optimum of 7.5–8, depending on the buffer used. It had apparent K m values for tryptophan and tetrahydrobiopterin of 49 μM and 32 μM respectively. The enzyme in chicken brain, but not rat brain, was cold‐shock labile but was stable for up to 4 days at — 20°C. Lability was observed both in tissues and homogenates of these tissues subjected to cold shock, but the extent of loss of activity varied between brain regions. Supernatant fractions did not lose activity after cold shock. The highest level of tryptophan hydroxylase was found in the rostral region of the chicken brainstem. High levels were also found in the caudal region of the brainstem, the midbrain, thalamus, caudate and cerebral cortex. The cerebellum and optic chiasma contained only traces of activity.