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STUDIES ON CELL METABOLISM AND CELL DIVISION : V. CYTOCHROME OXIDASE ACTIVITY IN THE EGGS OF ARBACIA PUNCTULATA
M E Krahl1, A K Keltch, C E Neubeck
1Lilly Research Laboratories, Indianapolis, Indiana, and the Marine Biological Laboratory, Woods Hole, Massachusetts.
The Journal of General Physiology
|October 30, 2009
Summary
Researchers isolated Arbacia egg cytochrome oxidase, finding it sufficient for egg respiration but not dependent on cytochrome c. Inhibitor studies revealed insights into respiration and cell division mechanisms in fertilized eggs.
Area of Science:
- Biochemistry
- Cellular Respiration
- Developmental Biology
Background:
- Cytochrome c oxidase is a key enzyme in cellular respiration, catalyzing the oxidation of cytochrome c.
- Understanding the role of cytochrome c oxidase in marine invertebrate eggs, like Arbacia, is crucial for elucidating developmental energy metabolism.
- Previous studies have explored respiratory inhibitors, but a comprehensive analysis in Arbacia eggs was lacking.
Purpose of the Study:
- To isolate and characterize cytochrome c oxidase from Arbacia eggs.
- To investigate the enzyme's kinetic properties and inhibition patterns.
- To determine the contribution of cytochrome c to overall egg respiration and its role in cell division.
Main Methods:
- Isolation and partial purification of cytochrome c oxidase from Arbacia eggs.
- Enzyme activity assays using various substrates and reductants (hydroquinone, p-phenylenediamine, cysteine).
- Inhibition studies using carbon monoxide, cyanide, azide, sulfide, and other potential inhibitors.
- Quantitative analysis of cytochrome c concentration in fertilized eggs.
- Assessment of the effects of azide and sulfide on egg respiration and cell division.
Main Results:
- Arbacia egg cytochrome oxidase was isolated and characterized, showing high affinity for cytochrome c.
- The enzyme was inhibited by carbon monoxide (reversible by light), cyanide, azide, and sulfide, but not by copper enzyme inhibitors or other tested compounds.
- Cytochrome c concentration in fertilized eggs was very low, indicating it does not significantly contribute to oxygen consumption.
- Inhibitory concentrations of azide and sulfide blocked cell cleavage while reducing respiration by approximately 50%.
Conclusions:
- Arbacia egg cytochrome oxidase is present in sufficient quantities to account for observed oxygen utilization.
- Cytochrome c is unlikely to be a significant respiratory carrier in these eggs.
- A distinct respiratory pathway, potentially involving a higher redox potential carrier, may be involved in energy supply for cell division.
