Free-radical metabolites can be generated metabolically by a one-electron reductase-catalyzed reaction or a "peroxidase" catalyzed oxidation or by photoactivation of a wide variety of aromatic xenobiotics. Radicals may also be generated during lipid peroxidation. Some radicals can react with DNA or bind covalently or noncovalently as a dismutation product or as a dimer, trimer or polymeric prod...

The biosynthesis of riboflavin requires 1 equivalent of GTP and 2 equivalents of ribulose phosphate. The first committed reactions of the convergent pathway are catalyzed by GTP hydrolase II and 3,4-dihydroxy-2-butanone 4-phosphate synthase. The initial reaction steps afford 5-amino-6-ribitylaminopyrimidine 5'-phosphate, which needs to be dephosphorylated by a hitherto elusive hydrolase. The de...

The Cu,ZnSODs (Cu,Zn superoxide dismutases) comprise a class of ubiquitous metalloenzymes that catalyse the dismutation of the superoxide radical anion into oxygen and hydrogen peroxide. The dismutation reaction involves two successive encounters of the superoxide anion with a catalytic copper centre hosted by the enzyme at the dead end of a narrow protein channel. Cu,ZnSOD is found in all euka...

Superoxide (O2 ) is the compound obtained when oxygen is reduced by one electron. For a molecule with an unpaired electron, O2 is surprisingly inert, its chief reaction being a dismutation in which it reacts with itself to form H2O2 and oxygen. The involvement of O2 in biological systems was first revealed by the discovery in 1969 of superoxide dismutase, an enzyme that catalyzes the dismutatio...

Previously it has been shown that Furacin (5-nitro-2-furaldehyde semicarbazone) inhibited the dismutation of pyruvate by whole resting cells of Micrococcus pyogenes var. aureus (1). Other earlier studies have also shown that both pyruvate dismutation and the formation of acetylmethylcarbinol (AMC) by cell-free extracts of pigeon breast muscle were markedly inhibited by Furacin (2). We are repor...

Reactions of primary imidazolio-phosphides (“imidazolylidene-phosphinidenes”) with R2SnCl2 yield as main products spectroscopically detectable Lewis pairs which undergo base-induced dehydrochlorination in the presence excess dichlorostannane to afford zwitterionic chloride adducts distannylated imidazolio-phosphines. In contrast, reactions R3SnCl proceed under dismutation furnish mixtures conta...

The chain reactions HO* + H2O2 --> H2O + O2*- + H+ and O2*- + H+ + H2O2 --> O2 + HO* + H2O, commonly known as the Haber-Weiss cycle, were first mentioned by Haber and Willstätter in 1931. George showed in 1947 that the second reaction is insignificant in comparison to the fast dismutation of superoxide, and this finding appears to have been accepted by Weiss in 1949. In 1970, the Haber-Weiss re...

Three mechanisms of oxygen reduction by chloroplast lamellae in the presence of autoxidizable electron acceptors can be differentiated by product analyis in the presence or absence of either dibromothymoquinone (DBMIB) or superoxide dismutase (SOD) : 1) H20 2 is the product of two-electron oxygen reduction by 2,3-dimethyl-5,6-methylenedioxy-pbenzoquinone, involving only photosystem II. This rea...

We examined the potential for CH4 oxidation to be coupled with oxygen derived from the dissimilatory reduction of perchlorate, chlorate, or via chlorite (ClO(-) 2) dismutation. Although dissimilatory reduction of ClO(-) 4 and ClO(-) 3 could be inferred from the accumulation of chloride ions either in spent media or in soil slurries prepared from exposed freshwater lake sediment, neither of thes...