Glu 69 is essential for the high sensitivity of muscle fructose-1,6-bisphosphatase inhibition by calcium ions.
Muscle fructose-1,6-bisphosphatase (FBPase) is highly sensitive toward inhibition by AMP and calcium ions. In allosteric inhibition by AMP, a loop 52-72 plays a decisive role. This loop is a highly conservative region in muscle and liver FBPases. It is feasible that the same region is involved in the inhibition by calcium ions. To test this hypothesis, chemical modification, limited proteolysis and site directed mutagenesis Glu(69)/Gln were employed. The chemical modification of Lys(71-72) and the proteolytic cleavage of the loop resulted in the significant decrease of the muscle FBPase sensitivity toward inhibition by calcium ions. The mutation of Glu(69)-->Gln resulted in a 500-fold increase of muscle isozyme I(0.5) vs. calcium ions. These results demonstrate the key role that the 52-72 amino acid loop plays in determining the sensitivity of FBPase to inhibition by AMP and calcium ions.
Zarzycki
Marek
M
Department of Animal Physiology, Zoological Institute, University of Wroclaw, Cybulskiego 30, 50-205 Wroclaw, Poland.
Maciaszczyk
Ewa
E
Dzugaj
Andrzej
A
D000249:Adenosine Monophosphate / Q000494:pharmacology; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology; D006597:Fructose-Bisphosphatase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics*; D005973:Glutamine / Q000737:chemistry / Q000235:genetics; D018482:Muscle, Skeletal / Q000201:enzymology*; D017354:Point Mutation; D011817:Rabbits
D002413:Cations, Divalent; D005973:Glutamine; D018698:Glutamic Acid; D000249:Adenosine Monophosphate; D006597:Fructose-Bisphosphatase; D002118:Calcium