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METAL CHELATES IN THE STORAGE AND TRANSPORT OF NEUROTRANSMITTERS: FORMATION OF MIXED LIGAND CHELATES OF Mg 2+ ‐ATP WITH BIOGENIC AMINES 1, 2
Author(s) -
Rajan K. S.,
Davis J. M.,
Colburn R. W.,
Jarke F. H.
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.tb01430.x
Subject(s) - chemistry , chelation , amine gas treating , metal , tyramine , ligand (biochemistry) , inorganic chemistry , magnesium , stability constants of complexes , medicinal chemistry , nuclear chemistry , stereochemistry , aqueous solution , organic chemistry , biochemistry , receptor
— Quantitative studies on the interactions of adenosine‐triphosphate and several biogenic amines with magnesium ion have been carried out in an attempt to correlate the thermodynamic stabilities of the metal‐binding of the amines with the in vivo affinities of the amines for granule‐binding. Equilibrium data indicate that in each of the ternary chelate systems ( viz. Mg 2+ ‐ATP‐amine), the predominant reaction in the pH range 3.0–7.0 is the formation of a magnesium‐ATP chelate with a stability constant, log K ML =3.22 ± 0.02. Each of the biogenic amines coordinates with Mg 2+ ‐ATP system in the pH range 7.0–10.5 to form the mixed ligand chelate (or ternary chelate), Mg 2+ ‐ATP‐amine(1:1:1). The stability constants for the binding of the amines with Mg 2+ ‐ATP are: (i) norepinephrine (NE) = 2.34 ± 0.32; (ii) epinephrine (E) = 2.95 ± 0.08; (iii) dopamine (DA) = 3.05 ± 0.06; (iv) octopamine (OA) = 1.93 ± 0.12; (v) 6‐hydroxydopamine (6‐HDA) = 2.42 ± 0.14; (vi) 3‐methoxynorephedrine (MeN) =2.76 ± 0.09; (vii) amphetamine (AA) =2.09 ± 0.05; (viii) tyramine (TA) = 2.60 ± 0.04; (ix) phenylethylamine (PEA) = 0. A general correlation is indicated between the stability constants (binding strengths) of the amine chelates and the metal‐binding functionalities of the amines on the one hand and their vesicular binding characteristics in in vivo systems on the other (C arlsson and W aldeck , 1966). The Mg 2+ ‐ATP‐dependant amine storage mechanism of KIRSHNER (1962 a;b ) and C arlsson , H illårp and W aldeck (1963) is discussed both in the light of the data on metal chelate stability and of a significant modification of metal coordination hypothesis.