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Lathyrus cicera copper amine oxidase reactions with tryptamine
Paola Pietrangeli1, Andrea Bellelli, Paola Fattibene
1Department of Biochemical Sciences, A. Rossi Fanelli, University of Rome Sapienza, P.le A. Moro 5, 00185 Rome, Italy. paola.pietrangeli@uniroma1.it
Journal of Inorganic Biochemistry
|February 29, 2012
Summary
Lathyrus cicera copper amine oxidase (LCAO) exhibits distinct catalytic mechanisms involving a Cu(II) species and a semiquinone radical. The Cu(II) derivative is linked to enzyme inactivation, while the radical is crucial for catalytic activity.
Area of Science:
- Biochemistry
- Enzymology
- Spectroscopy
Background:
- Copper amine oxidases (CAOs) are enzymes that catalyze the oxidation of primary amines.
- Lathyrus cicera copper amine oxidase (LCAO) is a specific CAO with unique properties.
- Understanding the catalytic mechanisms and active site dynamics of CAOs is crucial for enzyme engineering and drug development.
Purpose of the Study:
- To elucidate the reaction mechanism of Lathyrus cicera copper amine oxidase (LCAO).
- To characterize the spectral properties and roles of transient intermediates during LCAO catalysis.
- To investigate the relationship between enzyme activity, inactivation, and the observed spectral species.
Main Methods:
- UV-visible spectroscopy to monitor spectral changes during enzymatic turnover.
- Electron Paramagnetic Resonance (EPR) spectroscopy to characterize radical species.
- Enzyme kinetics to determine reaction rates and dependencies.
- Stopped-flow kinetics to study rapid reaction events.
Main Results:
- LCAO rapidly formed a Cu(I)-TPQ semiquinone spectrum upon O(2) depletion.
- A distinct Cu(II) species, absorbing at 630 nm, formed slowly and depended on aldehyde and H(2)O(2) concentrations.
- The Cu(II) species was associated with enzyme inactivation, while the semiquinone radical correlated with catalytic activity.
- Enzyme inactivation and spectral band decay occurred in parallel.
- Evidence suggests half-of-the-site reactivity in LCAO, with distinct subunit behavior.
Conclusions:
- The catalytic cycle of LCAO involves both a semiquinone radical essential for activity and a Cu(II) species implicated in inactivation.
- The formation of the Cu(II) species is dependent on reaction conditions, including aldehyde and H(2)O(2) levels.
- LCAO exhibits distinct kinetic and spectroscopic properties between its two subunits, consistent with half-of-the-site reactivity.
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