Phosphofructokinase from baker's yeast: kinetic properties of a proteolytically modified enzyme.
A tetrameric enzyme form of phosphofructokinase from yeast (called 12 S-enzyme), formed by limited proteolysis of the octameric enzyme in the presence of ATP and by subsequent dissociation in two half-molecules shows sigmoidal kinetics with respect to fructose 6-phosphate and inhibition by ATP. Similar to the native phosphofructokinase, the modified enzyme is also efficiently activated by AMP and fructose 2,6-bisphosphate. Both activators increase the affinity for the substrate fructose 6-phosphate and the respective maximum activity. In contrast to the native phosphofructokinase, however, both AMP and fructose 2,6-bisphosphate change the sigmoidal fructose 6-phosphate velocity curve into a hyperbolic one. AMP and fructose 2,6-bisphosphate decrease the ATP inhibition, probably by modulating the affinity of the allosteric sites to ATP.
Bär
J
J
Institut für Biochemie, Karl-Marx-Universität Leipzig, DDR.
Schellenberger
W
W
Kopperschläger
G
G
D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D004789:Enzyme Activation; D005636:Fructosephosphates / Q000378:metabolism; D007700:Kinetics; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D005636:Fructosephosphates; D000249:Adenosine Monophosphate; C027618:fructose-6-phosphate; D000255:Adenosine Triphosphate; D010732:Phosphofructokinase-1