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Oxygen Affinity of Tyrosine and Tryptophan Hydroxylases in Synaptosomes
Author(s) -
Katz Ira R.
Publication year - 1980
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.1471-4159.1980.tb03721.x
Subject(s) - tryptophan , tyrosine hydroxylase , tyrosine 3 monooxygenase , tyrosine , synaptosome , chemistry , biochemistry , oxygen , degree of unsaturation , biology , enzyme , in vitro , chromatography , amino acid , organic chemistry
: Tyrosine and tryptophan hydroxylase activities were studied in a synaptosome‐enriched (P 2 ) preparation from the rat striatum. Care was taken to avoid the potential diffusional artifacts to which measures of oxygenase activities in respiring tissue are, in general, subject. Tyrosine hydroxylase exhibited a K m for oxygen of 2 to 3 mm Hg under a variety of conditions. Tryptophan hydroxylase exhibited a K m of 3 to 4 mm Hg at C.S.F. levels of tryptophan (10 μ m ). The K m increased to 8 to 10 mm Hg at 2 μ m tryptophan. These values are all consistent with some degree of unsaturation with respect to oxygen in vivo .