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Cysteamine oxidation by lentil seedling amine oxidase
R Medda1, A Padiglia, A Lorrai
1Institute of Biological Chemistry, University of Cagliari, Italy.
Biochemistry and Molecular Biology International
|February 1, 1997
Summary
Lentil amine oxidase oxidizes cysteamine, but the resulting aldehyde inactivates the enzyme. Cysteamine also competitively inhibits amine oxidase when putrescine is the substrate.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Amine oxidase enzymes catalyze the oxidative deamination of amines.
- Cysteamine is a biologically relevant amine with potential interactions with amine oxidases.
Purpose of the Study:
- To investigate the oxidative deamination of cysteamine by lentil amine oxidase.
- To characterize the kinetics and inhibitory effects of cysteamine on amine oxidase activity.
Main Methods:
- Enzyme kinetics studies using lentil amine oxidase.
- Assays measuring amine oxidase activity with cysteamine and putrescine as substrates.
- Inhibition studies to determine kinetic parameters (Km, Ki).
Main Results:
- Cysteamine is a substrate for lentil amine oxidase, exhibiting saturation kinetics with a Km of 9 x 10(-4) M.
- The aldehyde product of cysteamine oxidation causes irreversible enzyme inactivation, which can be reversed by dialysis.
- Cysteamine acts as a competitive inhibitor of putrescine oxidation by amine oxidase, with a Ki of 5 x 10(-5) M.
Conclusions:
- Lentil amine oxidase catalyzes the oxidation of cysteamine.
- The aldehyde intermediate and thioacetaldehyde may play roles in enzyme activity modulation.
- Cysteamine's inhibitory effect suggests potential regulatory interactions within amine metabolism pathways.