Abstract
Electron spin resonance (ESR) oximetry technique was applied for analysis of catalase activity in the present study. Catalase activity was evaluated by measuring oxygen from the reaction between hydrogen peroxide (H2O2) and catalase-positive cells. It was demonstrated that the ESR spectra of spin-label probes, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL), 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (4-oxo-TEMPO) and 4-maleimido-2,2,6,6-tetramethyl-1-piperidinyloxy (4-maleimido-TEMPO) in the presence of H2O2 were broadened with the concentrations of catalase. It was possible to make a calibration curve for catalase activity by peak widths of the spectra of each spin-label probe, which are broadened dependently on catalase concentrations. The broadened ESR spectra were also observed when the catalase-positive micro-organisms or the mammalian cells originally from circulating monocytes/macrophages were mixed with TEMPOL and H2O2. Meanwhile, catalase-negative micro-organisms caused no broadening change of ESR spectra. The present study indicates that it is possible to evaluate directly the catalase activity of various micro-organisms and mammalian cells by using an ESR oximetry technique.
Acknowledgements
We would like to give our thanks to Professor Toshihiko Ozawa (Yokohama College of Pharmacy) for very insightful discussion.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
This paper was first published online on Early Online on 23 June 2010.