Glycogenolysis during recovery from muscular work. The time course of phosphorylase activity is dependent on Pi concentration in the abdominal muscle of the shrimp Crangon crangon.
1) Glycogen is degraded in the abdominal muscle of the shrimp Crangon crangon (Decapoda, Crustacea) during the recovery period following work. The regulation of post-exercise glycogen breakdown and the properties of glycogen phosphorylase (EC 2.4.1.1) have been studied: 2) Glycogen phosphorylase exists as unphosphorylated b-form and phosphorylated a-form, the latter contains 1 molecule phosphate/subunit. Both forms of phosphorylase are dimers, isoenzymes have not been detected. 3) The purified b-form is inactive in absence of AMP and has very low affinities for AMP and Pi. For half-maximum activation 0.33 +/- 0.04 mM AMP is necessary, and the Km-value for Pi at 1 mM AMP is 48 +/- 5 mM. IMP does not affect the activity of the b-form. 4) The a-form is active without effectors, its Km-value for Pi is 5.3 +/- 1.5 mM. The proportion of phosphorylase a increases in vivo, from about 25% at rest, to approximately 90% upon work and remains at this high level during the first minutes of recovery. 5) It is concluded that the glycogenolytic flux in the abdominal muscle of the shrimp even during post-exercise periods depends on the level of the a-form the activity of which is restricted in time and extent by the cytoplasmic Pi concentration (Kamp, G. & Juretschke, H. P. (1987) Biochim. Biophys. Acta 929, 121-127).
Zoologisches Institut der Universität Münster.
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D000249:Adenosine Monophosphate / Q000502:physiology; D000818:Animals; D033364:Decapoda / Q000502:physiology*; D004558:Electric Stimulation; D006003:Glycogen / Q000378:metabolism*; D007291:Inosine Monophosphate / Q000502:physiology; D007527:Isoenzymes / Q000032:analysis; D007700:Kinetics; D009132:Muscles / Q000502:physiology; D010710:Phosphates / Q000502:physiology; D010764:Phosphorylase Kinase; D006005:Phosphorylases / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation
D007527:Isoenzymes; D010710:Phosphates; D007291:Inosine Monophosphate; D000249:Adenosine Monophosphate; D006003:Glycogen; D006005:Phosphorylases; D010764:Phosphorylase Kinase