Nucleotide activation of glycogen phosphorylase b occurs only when the nucleotide phosphate is in a dianionic form

Adenosine monophosphofluoridate has been synthesised and purified to remove all contaminating AMP. This AMP analogue fails to activate glycogen phosphorylase b, even at high concentration, but inhibits the AMP activation with a Ki value of 3 mM. Activation of phosphorylase b by adenosine phosphorami...
Ausführliche Beschreibung

Adenosine monophosphofluoridate has been synthesised and purified to remove all contaminating AMP. This AMP analogue fails to activate glycogen phosphorylase b, even at high concentration, but inhibits the AMP activation with a Ki value of 3 mM. Activation of phosphorylase b by adenosine phosphoramidate has been re-investigated in the light of these findings and a purified sample of this nucleotide analogue has been shown to produce little or no activation of the enzyme. These findings are interpreted in terms of an absolute requirement of the nucleotide activatorsite in phosphorylase for a nucleotide with a dianionic phosphate. The implications of this for the role of the phosphate moiety in the proposed mechanism of activation are discussed. Ausführliche Beschreibung