STUDIES ON MECHANISM OF INACTIVATION OF CATECHOL 1,2-OXYGENASE BY ELECTRON SPIN RESONANCE

An electron spin resonance (ESR) spectrum of inactive catechol 1,2-oxygenase (catechol:O2 1,2-oxidoreductase, EC 1.13.1.1, formerly known as pyrocatechase) was measured and found to be an anisotropic one. These g-values were estimated to be gx = 3.87, gy = 4.41 and gz = 4.07, where as that of active catechol, 1,2-oxygenase is g = 4.28, which was degenerated. Comparing the theoretical g-values, which were calculated by AASA et al., with the experimental ones, the E- and D-terms in spin-Hamil-tonian were estimated to be 0.19 cm-l, respectively. From theoretical considerations, the inactivation mechanism seems to be the displacement of one of ligands on iron.