Characterization of peroxidase superoxide dismutase from dandelion (Taraxacum officinale) plant

Peroxidase (POD; EC 1.11.1.7) is an oxidoreductase that catalyses a reaction inwhich hydrogen peroxide acts as the acceptor and another compound acts as thedonor of hydrogen atoms.Superoxide dismutase (EC 1.15.1.1) are a class of enzymes that catalyze thedismutation of superoxide into oxygen and hydrogen peroxide.In this work, dandelion (Silybum marianum) was used for POD and SODcharacterization. POD activity was determined by measuring as indicated by anincrease in absorbance at 420 nm. Enzyme activity, as a function of pH, wasdetermined with substrate patterns (catechol, 4-methylcatechol, pyrogallol, caffeicacid, ABTS, gallic acid, guaiacol, o-dianisidine, o-phenilen diamin), in differentbuffer, ranging from pH 3,0 to 9,0. Enzyme activity, as a function of temperature,was determined with substrate patterns. Optimum temperature was found to changebetween 30 ? 40oC. Michaelis-Menten constant (Km) and maximum reaction velocity(Vmax) were determined using nine substrate patterns in nine different concentrationsfor the substrate specificity of POD. The substrate specificity of POD was found tobe caffeic acid, ABTS, o-dianisidine, gallic acid, pyrogallol, o-phenilen diamin, 4-methylcatechol, catechol and guaiacol, respectively for the plant. Eight inhibitorswere tested in the study and the effectives were found to be sodium azide, thiourea,ascorbic acid, 2-mercapto ethanol, L-Glutatyon and L-Cystein as competitiveinhibitors, potassium cyanide, as uncompetitive inhibitor, sodium sulfide asnoncompetitive inhibitor. In this study, superoxide dismutase (EC 1.15.1.1) Activitywas determined in the extract of dandelion (taraxacum officinale) with highantioxidant effect. After the ultracentrifugation step, superoxide dismutase spesificactivity was found. Optimum pH and optimum temperature were found to 7,6 and20oC.Peroxidase, superoxide dismutase, dandelion,antioxidant enzmys, free radicalsKey Words: Peroxidase, superoxide dismutase, dandelion, taraxacum officinale,antioxidant enzyms, free radicals,