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Human intestinal diamine oxidase: substrate specificity and comparative inhibitor study
Agents and Actions
|April 1, 1980
Summary
Human intestinal diamine oxidase prefers putrescine as a substrate. Its inhibition patterns suggest distinct enzyme functions, differentiating histamine detoxification from polyamine regulation.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Diamine oxidase (DAO) enzymes play crucial roles in metabolizing biogenic amines.
- Understanding human intestinal DAO specificity is vital for comprehending amine metabolism and detoxification pathways.
Purpose of the Study:
- To characterize the substrate and inhibitor specificity of purified human intestinal diamine oxidase.
- To differentiate functional roles of diamine oxidases based on their biochemical properties.
Main Methods:
- Purification of human intestinal diamine oxidase (80-fold).
- Assays to determine optimal incubation conditions, substrate preference, and inhibitor specificity.
- Comparative analysis with pea seedling diamine oxidase.
Main Results:
- Putrescine was the most favored substrate for human intestinal DAO.
- N tau-methylhistamine and 2-methylhistamine showed high metabolic velocity, while histamine was metabolized at 50% of putrescine's velocity.
- Aminoguanidine and semicarbazide acted as classical DAO inhibitors.
- Beta-aminopropionitrile and burimamide exhibited differential inhibition patterns between human intestinal and pea seedling DAO.
Conclusions:
- Human intestinal diamine oxidase exhibits distinct substrate and inhibitor profiles.
- These differences support the proposal to classify DAO enzymes based on their primary functions: histamine detoxification versus polyamine regulation in growing tissues.