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pH‐dependent release of catecholamines from tyrosine hydroxylase and the effect of phosphorylation of Ser‐40
Author(s) -
Haavik J.,
Martinez A.,
Fiatmark T.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80230-g
Subject(s) - tyrosine hydroxylase , chemistry , phosphorylation , tyrosine , protonation , dissociation (chemistry) , dissociation constant , reaction rate constant , tyrosine 3 monooxygenase , catecholamine , stereochemistry , kinetics , enzyme , endocrinology , medicine , biochemistry , biology , organic chemistry , ion , receptor , physics , quantum mechanics
Bovine adrenal tyrosine hydroxylase (TH) is isolated in a partially inhibited state with the feed‐back inhibitors adrenaline and noradrenaline tightly coordinated to high‐spin (S =) Fe(III) at the active site. In addition to the charge‐transfer interaction with iron, an additional charged group in the polypeptide chain, with an apparent p K a of about 5.3 at 4°C, is involved in the binding of catecholamines. Protonation of this group increases the pseudo‐first order rate constant for the dissociation of the TH‐[ 3 H]noradrenaline complex more than 100‐fold at 4°C. At pH 7.0 and 30°C, phosphorylation of Ser‐40 causes a 6‐fold increase in the rate constant for this dissociation.