Pyrophosphate functions as phosphoryl donor with UDP-glucose-treated mammalian phosphofructokinase.

Phosphofructokinase of rabbit muscle, which is specific for nucleoside triphosphates such as ATP, dissociated and gained the capability to utilize pyrophosphate as phosphoryl donor following incubation with UDP-glucose. The pyrophosphate- and ATP-linked activities of UDP-glucose-treated muscle phosphofructokinase were promoted by a protein species that showed a molecular weight of 80 kDa (vs. 320 kDa for the untreated enzyme). In the presence of citrate, a known inhibitor of PFK, the pyrophosphate-dependent activity elicited by UDP-glucose treatment was activated by fructose-2,6-bisphosphate. On removal of the UDP-glucose by either dialysis or dilution, the treated enzyme reassociated and became ATP-specific. ATP, dithiothreitol, and fructose-2,6-bisphosphate stimulated reassociation. The results suggest that metabolite-mediated catalyst conversion, yielding an enzyme form capable of utilizing both ATP and pyrophosphate, takes place with the phosphofructokinases of animal tissues.