Light emission from tryptophan oxidation by hypobromous acid
Maicon Segalla Petrônio1, Valdecir Farias Ximenes
1Departamento de Química, Faculdade de Ciências, Universidade Estadual Paulista, Bauru, Sao Paulo, Brazil; Departamento de Análises Clínicas, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, Araraquara, Sao Paulo, Brazil.
Summary
Oxidation of tryptophan by hypobromous acid generates ultraweak cellular light emission. This process, enhanced by taurine, suggests tryptophan
Area of Science:
- Biochemistry
- Cellular Biology
- Spectroscopy
Background:
- Ultraweak light emission from cells is linked to biomolecule oxidation by reactive oxygen species.
- The indole group in molecules like tryptophan, serotonin, and melatonin is often involved in light emission during oxidation.
Purpose of the Study:
- To investigate hypobromous acid (HOBr) oxidation of tryptophan as a potential endogenous source of ultraweak light emission.
- To compare the chemiluminescence generated by HOBr and hypochlorous acid (HOCl) oxidation of tryptophan.
- To elucidate the mechanism behind the observed differences in light emission.
Main Methods:
- Oxidation of tryptophan using hypobromous acid (HOBr) and hypochlorous acid (HOCl).
- Analysis of oxidation products and chemiluminescence intensity.
- Investigation of the role of the free α-amino group in light emission.
- Evaluation of taurine monobromamine and dibromamine as oxidants.
Main Results:
- HOBr oxidation of tryptophan produced significantly higher chemiluminescence than HOCl.
- Secondary oxidation reactions were more intense with HOBr.
- Specific oxidation products (e.g., N-formylkynurenine) were identified with HOCl but depleted with HOBr.
- Light emission depended on the free α-amino group of tryptophan; serotonin and melatonin did not produce chemiluminescence.
- Taurine bromamines resulted in even greater light emission compared to HOBr.
Conclusions:
- Oxidation of free tryptophan or tryptophan residues in proteins is a significant source of ultraweak cellular light emission.
- The mechanism likely involves bromine radical intermediates, explaining the higher efficiency with HOBr.
- Taurine enhances this light emission, making it particularly relevant in leukocytes.
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