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Updated: Aug 21, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Calcium inhibits muscle FBPase and affects its intracellular localization in cardiomyocytes
1Department of Animal Physiology, Institute of Zoology, Wroclaw University, Cybulskiego 30, 50-205 Wroclaw, Poland.
Abstract:
As our recent investigation revealed, in mammalian heart muscle, fructose 1,6-bisphosphatase (FBPase)--a key enzyme of glyconeogenesis--is located around the Z-line, inside cells' nuclei and, as we demonstrate here for the first time, it associates with intercalated discs. Since the degree of association of numerous enzymes with subcellular structures depends on the metabolic state of the cell, we studied the effect of elevated Ca2+ concentration on localization of FBPase in cardiomyocytes. In such conditions, FBPase dissociated from the Z-line, but no visible effect on FBPase associated with intercalated discs or on the nuclear localization of the enzyme was observed. Additionally, Ca2+ appeared to be a strong inhibitor of muscle FBPase.
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