Glycogen phosphorolysis can form a metabolic shuttle to support Ca2+ uptake by sarcoplasmic reticulum membranes in skeletal muscle.
In the presence of glycogen, ADP, phosphoglucomutase and hexokinase, the glycogen phosphorylase b activity associated to sarcoplasmic reticulum (SR) membranes stimulates Ca2+ uptake by SR membrane fragments in the absence of added ATP. Phosphoglucomutase and hexokinase lead to the formation of glucose 6-phosphate which in turn is used as an ATP regenerating system by the Ca2+ pump. It is proposed that a raise of cytosolic AMP and ADP concentrations after muscle contraction can activate an alternative metabolic route which would be used to ensure the maintenance of a low cytosolic Ca2+ concentration and avoid unnecessary metabolic energy depletion in muscle cells.
Cuenda
A
A
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
Nogues
M
M
Gutiérrez-Merino
C
C
de Meis
L
L
D000249:Adenosine Monophosphate / Q000378:metabolism / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D010733:Phosphoglucomutase / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D002110:Caffeine; D000249:Adenosine Monophosphate; D006003:Glycogen; D006005:Phosphorylases; D006593:Hexokinase; D000251:Adenosine Triphosphatases; D010733:Phosphoglucomutase; D002118:Calcium