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ALLOSTERIC ACTIVATION OF HYPOTHALAMIC TYROSINE HYDROXYLASE BY IONS AND SULPHATED MUCOPOLYSACCHARIDES
Author(s) -
Kuczenski R. T.,
Mandell A. J.
Publication year - 1972
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.1471-4159.1972.tb01262.x
Subject(s) - tyrosine hydroxylase , glycosaminoglycan , allosteric regulation , chemistry , enzyme , tyrosine , heparin , biochemistry , tyrosine 3 monooxygenase
— The kinetics of canine hypothalamic tyrosine hydroxylase were studied in the presence of various ions and sulphated mucopolysaccharides. Enzymic activity was dependent on ionic strength, a specific sulphate effect and the presence of the highly sulphated mucopolysaccharide, heparin. Whereas both sulphate and heparin activated tyrosine hydroxylase by increasing V max heparin, but not sulphate, also increased the affinity of the enzyme for the synthetic cofactor, 2‐amino‐4‐hydroxy‐6,7‐dirnethyl‐5,6,7,8‐tetrahydropteridine, by nearly an order of magnitude. Other rnucopolysaccharides, such as chondroitin sulphate and hyaluronic acid, were not effective as activators of tyrosine hydroxylase. The allosteric activation of tyrosine hydroxylase by heparin may serve to ‘sensitize’ the enzyme to low levels of its end product, norepinephrine.