Rabbit muscle fructose-1,6-bisphosphatase is phosphorylatedin vivo.
Phosphorylated fructose-1,6-bisphosphatase (FBPase) was isolated from rabbit muscle in an SDS/PAGE homogeneous form. Its dephosphorylation with alkaline phosphatase revealed 2.8 moles of inorganic phosphate per mole of FBPase. The phosphorylated FBPase (P-FBPase) differs from the dephosphorylated enzyme in terms of its kinetic properties like K(m) and k(cat), which are two times higher for the phosphorylated FBPase, and in the affinity for aldolase, which is three times lower for the dephosphorylated enzyme. Dephosphorylated FBPase can be a substrate for protein kinase A and the amount of phosphate incorporated per FBPase monomer can reach 2-3 molecules. Since interaction of muscle aldolase with muscle FBPase results in desensitisation of the latter toward AMP inhibition (Rakus & Dzugaj, 2000, Biochem. Biophys. Res. Commun. 275, 611-616), phosphorylation may be considered as a way of muscle FBPase activity regulation.
Rakus
Dariusz
D
Department of Animal Physiology, Zoological Institute, University of Wrocław, Z Cybulskiego 30, 50-205 Wrocław, Poland.
Zarzycki
Marek
M
Dzugaj
Andrzej
A
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006597:Fructose-Bisphosphatase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D018482:Muscle, Skeletal / Q000201:enzymology*; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011817:Rabbits; D013379:Substrate Specificity
D010710:Phosphates; D017868:Cyclic AMP-Dependent Protein Kinases; D006597:Fructose-Bisphosphatase