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Chicken ornithine transcarbamylase: its unexpected expression
Biochemical Genetics
|April 1, 1987
Summary
Chicken kidneys contain ornithine transcarbamylase (OTC), an enzyme not typically found in their non-functional urea cycle. A precursor form is present in various organs, with kidney extract activating it, suggesting tissue-specific processing.
Area of Science:
- Biochemistry
- Molecular Biology
- Comparative Physiology
Background:
- Ornithine transcarbamylase (OTC) is a key urea cycle enzyme, typically found in the mitochondria of the kidney.
- Chickens lack a functional urea cycle, yet OTC and its precursor are detectable in various tissues.
Purpose of the Study:
- To investigate the presence and processing of ornithine transcarbamylase (OTC) in chickens.
- To determine if chicken tissues can process the precursor form of OTC into its active enzyme.
Main Methods:
- Immunoabsorbent column chromatography was used to detect OTC and its precursor forms.
- Tissue extracts from various chicken organs were analyzed for OTC presence and activity.
- Incubation of precursor OTC with kidney extract was performed to assess processing.
Main Results:
- A precursor form of ornithine transcarbamylase (40 kd) was detected in chicken brain, heart, liver, pancreas, gizzard, small intestine, and breast muscle.
- The active form of OTC (36 kd subunits) was primarily found in kidney mitochondria.
- Kidney extract converted the precursor OTC from the small intestine into the active enzyme form.
Conclusions:
- A kidney-specific protease likely processes the precursor OTC, activating it in this organ.
- Chickens exhibit organ-specific mechanisms for precursor OTC processing and mitochondrial import, differing from mammals.