Synthesis of Glucose 1,6‐Bisphosphate by the Action of Crystalline Rabbit Muscle Phosphofructokinase

Abstract

Crystalline rabbit muscle phosphofructokinase catalyzes the transfer of the γ‐phosphate of ATP to glucose‐1‐phosphate in the presence of Mg 2+ . The reaction product was characterized as glucose 1,6‐bisphosphate by evaluation of hydrolysis data and by means of enzymatic and chromatographic analyses. The enzyme responsible for this “glucose‐1‐phosphate kinase” reaction is most probably identical with phosphofructokinase. The activities of glucose‐1‐phosphate kinase and phosphofructokinase show identical behaviour during purification, anion exchange chromatography and sucrose density gradient centrifugation; furthermore the stability of glucose‐1‐phosphate kinase is highly correlated to that of phosphofructokinase. It is concluded from experiments in vitro that the glucose‐1‐phosphate kinase reaction is the main route for glucose‐1,6‐bisphosphate synthesis in rabbit skeletal muscle. This reactions seems to be more significant than other pathways discussed in the literature, e.g. transphosphorylation from fructose‐1,6‐bisphosphate to glucose‐6‐phosphate (or glucose‐1‐phosphate) as catalyzed by phosphoglucomutase.