Peroxidase activity of germinatingSorghum bicolorgrains: effect of some cations

Abstract

We investigated some properties of the major ionic peroxidase (POD) from germinating Sorghum bicolor var Fara Fara. Peroxidase activity increased eightfold during the ®rst 36 h of germination and declined thereafter to four times the value in the dry grain after 144 h. Gel ®ltration followed by ion exchange chromatography resolved the major peroxidase into two forms. The predominant POD had an optimum temperature of 55°C, two pH optima at 5.0 and 7.0, with a sharp decline in activity below pH 4.5, an apparent activation energy of 463 kJ mol À1 , an apparent molecular weight of 63.1 kDa and was relatively heat-stable up to 70°C. The enzyme was strongly inhibited by dithiothreitol and sodium metabisulphite. Calcium chloride and magnesium chloride below 2 mM enhanced POD activity without any adverse effect on germination, while ammonium chloride and ferric chloride inhibited the enzymatic activity of both forms. At 5 mM, magnesium chloride inhibited POD activity by 50% with only a 14% reduction in germination, while calcium chloride achieved the same effect at 10 mM. These results are pertinent to controlling the undesirable activity of peroxidase in a typical malting or brewing process.

Impact of Germination on Biochemical and Antioxidant Enzymes of Ceiba pentandra (Kapok) Seeds

“…Moreover, PODs probably play an important role in seed germination, growth, morphogenesis, and even in the final stage of senescence and death [29,30]. Changes in PODs activities occur during developmental process in tissue specific manner and differential regulation in response to germination process and plant species has been reported [31,32]. The present results indicate that PODs activities in the degrading endosperms and developing cotyledons were considerably greater than those of the raw seeds.…”

Responses of bioenergy sorghum cell wall metabolism to agronomic practices

“…Most of the inactive isoenzymes were acidic (pI < 4.0), and the active isoenzymes (boxed) had higher pI values. Chromatographic and two-dimensional purification procedures had been inadequate for concentrating the active isoenzymes, and removing them from the inactive forms [23][24][25]. Native polyacrylamide gel electrophoresis (PAGE) of the Rotofor fractions revealed the two groups (anionic and cationic) of isoenzymes that make up the charge isomers (Figures 1-4).…”

Purification of Active Peroxidase Isoenzymes and Their Responses to Nitrogen Fertilization and Rotation of Biomass Sorghum

“…Peroxidase (EC 1.11.1.7; donor: hydrogen peroxide oxidoreductase) isoenzymes are ubiquitous in plant cells and tissues; and display many isoenzymic forms, up to 15 proteins in alfalfa [1]. They contain heme iron, Ca 2+ , Mn 2+ , Mg 2+ , Cu 2+ etc prosthetic groups [2,3] and catalyze the oxidation of diverse electron donor substrates (aromatic amines, phenols etc.) using hydrogen peroxide as the terminal electron acceptor [4].…”

“…The kinetic properties of crystalline peroxidases have been studied [12], the overall oxidoreductase reactions being dominated by the formation of two intermediate complexes (oxidized peroxidase, and partially reduced peroxidase): 2…”