Abstract
We investigated some properties of the major ionic peroxidase (POD) from germinating Sorghum bicolor var Fara Fara. Peroxidase activity increased eightfold during the first 36βh of germination and declined thereafter to four times the value in the dry grain after 144βh. Gel filtration followed by ion exchange chromatography resolved the major peroxidase into two forms. The predominant POD had an optimum temperature of 55βΒ°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 463βkJβmol^β1^, an apparent molecular weight of 63.1βkDa and was relatively heatβstable up to 70βΒ°C. The enzyme was strongly inhibited by dithiothreitol and sodium metabisulphite. Calcium chloride and magnesium chloride below 2βmM enhanced POD activity without any adverse effect on germination, while ammonium chloride and ferric chloride inhibited the enzymatic activity of both forms. At 5βmM, magnesium chloride inhibited POD activity by 50% with only a 14% reduction in germination, while calcium chloride achieved the same effect at 10βmM. These results are pertinent to controlling the undesirable activity of peroxidase in a typical malting or brewing process.
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