The control of glycolysis in aged slices of carrot root tissue

The possibility that the rate of glycolysis in aged slices of carrot (Daucus carota L.) is controlled by the enzyme phosphofructokinase was examined, by changing the rate of metabolism, by supplying the tissue with potassium chloride, potassium phosphate and potassium citrate and measuring the subsequent changes in levels of metabolites. Potassium chloride and potassium phosphate stimulate glycolysis, potassium citrate inhibits glycolysis and the associated changes in metabolites are consistent with the view that respiration is controlled by a dual system involving phosphofructokinase and glyceraldehyde phosphate dehydrogenase or possibly phosphoglycerate kinase. It is proposed that the control points are interlocked by phosphoenolpyruvate and phosphoglycerate. Thus if glyceraldehyde phosphate dehydrogenase is activated leading to an accumulation of phosphoglycerate and phosphoenolpyruvate, these compounds will inhibit phosphofructokinase. Thus our proposal for metabolic control in carrot resembles those proposed in mammalian systems except that the negative feedback system involving ATP and AMP which controls phosphofructokinase in mammals is replaced by a negative feedback system involving phosphoenolpyruvate and phosphoglycerate.