TPNH and pyridoxal-5′-phosphate: Activators of ADP-glucose pyrophosphorylase of Escherichia coli B

Abstract

TPNH and pyridoxal-5-P have been found to be potent activators of E. coli B ADP-glucose pyrophosphorylase. The concentrations required for 50% maximal activation was 0.15 mM TPNH and 8 μM pyridoxal-5-P. These values compare favorably to the value of 0.13 mM found previously for the activator, fructose diP. Kinetic evidence is presented to suggest all three activators bind to the same site(s) on the enzyme. PLP-activated ADP-glucose synthesis is less sensitive to 5′-adenylate inhibition than is TPNH-activated synthesis. The physiological functions of these activations with respect to glycogen storage is discussed.