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The effect of ions on the enzymatic properties of beef‐liver glutamate dehydrogenase
Author(s) -
Blauer G.,
Sund H.
Publication year - 1977
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1977.360160508
Subject(s) - chemistry , glutamate dehydrogenase , enzyme , thiocyanate , inorganic chemistry , dissociation constant , cofactor , ion , dissociation (chemistry) , stereochemistry , medicinal chemistry , organic chemistry , glutamate receptor , biochemistry , receptor
The effect of various salts on the enzymatic activity of beef‐liver glutamate dehydrogenase, on the binary enzyme‐reduced coenzyme (NADH or NADPH) comples, as well as on the ternary complex with glutamate was investigated in aqueous solution (0.067 M phosphate buffer, pH 7.6). Binding studies in the analytical ultracentrifuge and circular dichroism measurements indicated dissociation of the coenzyme from the enzyme‐coenzyme complex by the action of various salts. The efficiency of this change was largely dependent on the type of anion present and generally followed the series: acetate < Br − < I − < SCN − . Acetate ions and guanidinium thiocyanate showed exceptional behaviour in some cases, while K + and Na + gave similar results. The reversibility of the ion effects on the enzymatic activity was demonstrated by dilution tests. Upon addition of salts, the inhibitory effect of GTP was slightly changed in most cases, while the activating effects of ADP and L ‐leucine were practically abolished and with ADP, the halides caused an additional inhibition. Assuming an equilibrium involving dissociation of the enzyme‐coenzyme complex by the action of salts, an exponent of 1.3 for NaBr and of 2.0 for KSCN was calculated for the respective concentrations. The apparent equilibrium constants were evaluated to be about 20 times greater for KSCN than for NaBr.