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Rat brain aspartate ?-decarboxylase. A comparative study with the liver enzyme
1Department of Pharmacology, Faculty of Medicine, National Univesity of Singapore, Kent Ridge, Singapore 0511, Republic of Singapore.
Neurochemistry International
|May 25, 2010
Summary
Aspartate ?-decarboxylase (AspD) is primarily found in the brain, kidney, and liver. Enzyme activity varies across brain regions, and kinetic analysis suggests the presence of multiple AspD isozymes.
Area of Science:
- Biochemistry
- Enzymology
- Neurochemistry
Background:
- Aspartate ?-decarboxylase (AspD) catalyzes the conversion of aspartate to alanine.
- AspD is found in significant quantities in the brain, kidney, and liver, with optimal activity at pH 7.4.
Purpose of the Study:
- To investigate the distribution and kinetic properties of Aspartate ?-decarboxylase (AspD).
- To explore potential isozymes of AspD based on varying kinetic parameters and inhibition patterns.
Main Methods:
- Enzyme activity assays across different brain regions, liver, and kidney.
- Kinetic analysis including K(m) and V(max) determination.
- Inhibition studies using various amino acids and aminooxyacetic acid.
Main Results:
- AspD activity showed an 8-fold variation across seven brain regions, with highest levels in the cortex.
- Liver and kidney AspD exhibited identical affinity for aspartate (K(m) = 3.5 mM), while brain AspD had a higher affinity (K(m) = 1.3 mM).
- Differential inhibition and activation by serine, along with varying kinetic parameters, suggest the existence of multiple AspD isozymes.
Conclusions:
- Aspartate ?-decarboxylase (AspD) exhibits tissue-specific distribution and kinetic properties.
- Evidence strongly suggests that AspD exists as two or more isozymes with distinct characteristics in different organs.
