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Essential arginyl residues in mitochondrial adenosine triphosphatase
The Journal of Biological Chemistry
|March 25, 1976
Summary
Arginine residues are crucial for mitochondrial ATPase function. Chemical modification of these residues with reagents like 2,3-butanedione inactivates the enzyme, indicating their essential role at the hydrolytic site.
Area of Science:
- Biochemistry
- Enzymology
- Mitochondrial Function
Background:
- Mitochondrial ATPase (ATP synthase) is vital for cellular energy production.
- The specific roles of amino acid residues in ATPase activity are not fully elucidated.
Purpose of the Study:
- To investigate the role of arginyl residues in mitochondrial ATPase activity.
- To determine the effect of chemical modification of arginine on enzyme function.
Main Methods:
- Enzyme inactivation studies using arginine-specific reagents (2,3-butanedione, phenylglyoxal) on beef heart and rat liver mitochondrial ATPase.
- Kinetic analysis of enzyme activity before and after modification.
- Measurement of [14C]phenylglyoxal incorporation.
Main Results:
- 2,3-butanedione rapidly inactivated mitochondrial ATPase, following pseudo-first order kinetics.
- ATP protected the enzyme from inactivation, suggesting the active site is involved.
- Inactivation did not result from subunit dissociation, and kinetic parameters (Km) remained largely unchanged.
- Arginine modification was confirmed by phenylglyoxal incorporation.
Conclusions:
- Arginyl residues are essential for mitochondrial ATPase activity.
- These residues likely play a critical role at the enzyme's hydrolytic site.