Abstract
Abstract The kinetics and mechanism of action of rabbit skeletal muscle phosphofructokinase (ATP:d-fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.11) were investigated by several techniques. The initial velocity, product inhibition, isotope exchange patterns, and the result of a pulse labeling experiment are consistent with a mechanism in which ADP (or inosine diphosphate) dissociates from the enzyme before the addition of fructose 6-phosphate, and suggest the formation of phosphoryl enzyme as an intermediate. The enzyme preparation shows ATPase and fructose diphosphatase activities. The ATPase activity is catalyzed by the same protein that catalyzes the phosphofructokinase reaction.
Highlights
EC 2.7.1.11) were investigated by several techniques
Fructose-6-P concentrations were varied at fixed concentrations of ITP, double reciprocal plots exhibited essentially parallel lines (Fig. 2)
These results seem to suggest that the two substrates, ITP and fructose-6-P, are not present simultaneously on the enzyme, since the lines do not converge at a common point
Summary
The kinetics and mechanism of action of rabbit skeletal muscle phosphofructokinase 1 -phosphotransferase, EC 2.7.1.11) were investigated by several techniques. The initial velocity, product inhibition, isotope exchange patterns, and the result of a pulse labeling experiment are consistent with a mechanism in which ADP techniques: (a) kinetic behavior using inosine triphosphate as substrate, which avoids the allosteric effect of ATP; (b) product inhibition studies; (c) studies of the ATP-ADP exchange and of the exchange reactions of fructose-l ,6&P with fructose-6-P; (d) pulse labeling experiments with 32P-ATP
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