Phosphorylase Inhibitor in Potato: Separation from Activator and Possible Relation to Chlorogenic Acid

Abstract

IN a previous study of the factors in ethanolic extracts of potato which influence the activity of potato phosphorylase, it was found that although the observed shortening of the amylose chains synthesized by this enzyme could, in part, be attributed to the presence of inorganic orthophosphate in the extracts, the latter did not cause an inhibition of phosphorylase as measured by the rate of liberation of phosphate from glucose-1-phosphate in the presence of starch primer¹. However, demonstration of primer (activator) activity of such extracts after de-ionization with ion-exchange resin implied the presence of true inhibitory activity in the extracts. Presumably this inhibitory action is obscured by the presence of activator (primer). Since no inhibitory activity could be demonstrated in the acid or alkaline eluates from cation-exchange columns after chromatography of the potato extracts, it would appear that the inhibitor is acidic. However, attempts to recover inhibitory activity in acid eluates from anion-exchange chromatography of the extracts was complicated by the appearance in these eluates of trace amounts of material, derived from the columns, which in themselves possessed considerable inhibitory activity. In the case of weak phenolformaldehyde resins, the inhibition was traced to the inactivating effect of formaldehyde, whereas polystyrene-quaternary amine resins yielded a green non-fluorescent material devoid of nitrogen which also exhibited inhibitory activity. Pretreatment of the resins under a variety of conditions did not eliminate subsequent elution of inhibitory material.