Phosphate exchange between high-energy phosphate compounds in resting crustacean muscle
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Abstract:
Single giant muscle fibres from Megabalamus psittacus was microinjected with ATP-32P or internally perfused with a solution containing 32P-PArg in an attempt to demonstrate, in the absence of inhibitiors, ATP utilization during mechanical activity with negative results. The rate constant of transfer of 32P from microinjected 32P-PArg to endogenous ATP was studied at two different temperatures, obtaining a Q10 of 1.08 +/- .012. It is concluded that the rate limiting step in the process of transference of phosphate in the resting muscle from balanus is the intracellular diffusion of PArg and not the rate at which the equivalent of Lohman's reaction in invertebrates proceeds.
Insights
Phosphate transfer in Megabalamus psittacus muscle is limited by PArg diffusion, not ATP utilization during activity. This study investigated ATP utilization and phosphate transfer in invertebrate muscle fibers.
Area of Science:
- Marine biology
- Muscle physiology
- Biochemistry
Background:
- Understanding energy metabolism in invertebrate muscle is crucial.
- The role of ATP utilization and phosphate transfer in muscle contraction requires elucidation.
Purpose of the Study:
- To investigate ATP utilization during mechanical activity in Megabalamus psittacus muscle fibers.
- To determine the rate-limiting step in phosphate transfer within these muscle fibers.
Main Methods:
- Microinjection of ATP-32P and perfusion with 32P-PArg into single giant muscle fibers.
- Measurement of 32P transfer rate constants from PArg to ATP at different temperatures.
- Calculation of Q10 values to assess temperature dependence.
Main Results:
- No significant ATP utilization was detected during mechanical activity in the absence of inhibitors.
- The rate constant for 32P transfer from PArg to ATP showed a Q10 of 1.08 +/- 0.012.
- Intracellular diffusion of PArg was identified as the rate-limiting step for phosphate transfer.
Conclusions:
- ATP utilization is not the primary driver of mechanical activity under the tested conditions.
- Phosphate transfer in resting Megabalamus psittacus muscle is primarily limited by PArg diffusion, not the Lohmann reaction.
- These findings provide insights into the bioenergetics of invertebrate muscle function.