Different sensitivities of mutants and chimeric forms of human muscle and liver fructose-1,6-bisphosphatases towards AMP.
AMP is an allosteric inhibitor of human muscle and liver fructose-1,6-bisphosphatase (FBPase). Despite strong similarity of the nucleotide binding domains, the muscle enzyme is inhibited by AMP approximately 35 times stronger than liver FBPase: I0.5 for muscle and for liver FBPase are 0.14 microM and 4.8 microM, respectively. Chimeric human muscle (L50M288) and chimeric human liver enzymes (M50L288), in which the N-terminal residues (1-50) were derived from the human liver and human muscle FBPases, respectively, were inhibited by AMP 2-3 times stronger than the wild-type liver enzyme. An amino acid exchange within the N-terminal region of the muscle enzyme towards liver FBPase (Lys20-->Glu) resulted in 13-fold increased I0.5 values compared to the wild-type muscle enzyme. However, the opposite exchanges in the liver enzyme (Glu20-->Lys and double mutation Glu19-->Asp/Glu20-->Lys) did not change the sensitivity for AMP inhibition of the liver mutant (I0.5 value of 4.9 microM). The decrease of sensitivity for AMP of the muscle mutant Lys20-->Glu, as well as the lack of changes in the inhibition by AMP of liver mutants Glu20-->Lys and Glu19-->Asp/Glu20-->Lys, suggest a different mechanism of AMP binding to the muscle and liver enzyme.
Rakus
Dariusz
D
Department of Animal Physiology, Zoological Institute, Wroclaw University, Cybulskiego 30, 50-205 Wroclaw, Poland.
Tillmann
Harald
H
Wysocki
Robert
R
Ulaszewski
Stanislaw
S
Eschrich
Klaus
K
Dzugaj
Andrzej
A
D000249:Adenosine Monophosphate / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004926:Escherichia coli / Q000378:metabolism; D006597:Fructose-Bisphosphatase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008958:Models, Molecular; D008968:Molecular Conformation; D018482:Muscle, Skeletal / Q000201:enzymology*; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000502:physiology*; D009243:NAD / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics*
D017931:DNA Primers; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D009243:NAD; D000249:Adenosine Monophosphate; D006597:Fructose-Bisphosphatase; D008274:Magnesium