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Glu 69 is essential for the high sensitivity of muscle fructose‐1,6‐bisphosphatase inhibition by calcium ions
Author(s) -
Zarzycki Marek,
Maciaszczyk Ewa,
Dzugaj Andrzej
Publication year - 2007
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2007.02.051
Subject(s) - fructose 1,6 bisphosphatase , calcium , chemistry , biochemistry , allosteric regulation , fructose , proteolysis , enzyme , biophysics , biology , organic chemistry
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.