Carbamylphosphate hydrolysis in donkey liver
The Italian Journal of Biochemistry
|May 1, 1976
Summary
Mitochondria, microsomes, and cytosol enzymes hydrolyze carbamylphosphate, with microsomes exhibiting the highest activity. Differences in pH optima and heat stability distinguish mitochondrial and cytosol enzymes.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Carbamylphosphate hydrolysis is a key metabolic process.
- Enzymes in different cellular compartments play crucial roles in biochemical pathways.
Purpose of the Study:
- To investigate and compare the carbamylphosphate hydrolyzing enzymes found in mitochondria, microsomes, and cytosol.
- To characterize the kinetic and physical properties of these enzymes.
Main Methods:
- Enzyme activity assays were performed on mitochondrial, microsomal, and cytosol fractions.
- Optimum pH, heat stability, and substrate inhibition kinetics were determined for the enzymes.
- Kinetic parameters (Km) for carbamylphosphate were measured.
Main Results:
- All three cellular fractions (mitochondria, microsomes, cytosol) possess carbamylphosphate hydrolyzing activity.
- Microsomes displayed the highest specific activity.
- Mitochondrial enzyme: inner membrane localization, pH optimum 5.5, heat-stable.
- Cytosol enzyme: pH optimum 5.0, heat-labile.
- Both mitochondrial and cytosol enzymes showed a Km of 1.1-1.2 X 10(-2) M for carbamylphosphate.
- High substrate concentrations inhibited both enzymes.
Conclusions:
- Distinct enzymatic activities for carbamylphosphate hydrolysis exist in mitochondria, microsomes, and cytosol.
- The mitochondrial and cytosol enzymes exhibit differential properties, suggesting distinct biological roles.
- Kinetic analysis reveals similarities in substrate affinity but differences in stability and optimal conditions.
