Studies in bioluminescence. 10. Chemical models of enzymic oxidations.
Summary Oxidation of Pholad luciferin, luminol and a wide range of other compounds by superoxide ion produced electrolytically or by oxidation of H 2 O 2 with sodium periodate is described. Similar behaviour is shown by reduced FMN, or by ferrous ions and a phosphate ligand, in the presence of oxygen and it is shown that such systems are strongly oxidative due to a one electron reduction of dissolved molecular oxygen to O 2 ⨪rather than to production of hydrogen peroxide. Thus although catalase shows little or no effect on the oxidation, superoxide dismutase strongly inhibits. The general characteristics of the FMNH 2 /O 2 and Fe 2+ /O 2 / phosphate systems as a function of pH and of other parameters are described. In the absence of substrate, all four systems mentioned emit light (at a very low level) due to decomposition of the superoxide ions produced, presumably via excited singlet oxygen molecules.