Peroxidase isozymes from cassava (Manihot esculenta Crantz.) roots during postharvest deterioration
1998
Thakorn Sornwatana | Montri Chulavatnatol (Mahidol Univ., Bangkok (Thailand). Faculty of Science. Dept. of Biochemistry)
Previous studies have shown that peroxidase increases during post-harvest deterioration and discolouration of cassava tubers. Using non-denaturation gel electrophoresis (ND), cassava peroxidase was separated into 3 groups; positively charged, negatively charged and neutral isozymes cassava roots after storage for 7 days showed increases in the positively charged peroxidase of both the cortex and the parenchyma. In contrast, the negatively charged and neutral peroxidases of both the cortex and the parenchyma decreased. Further charaterization of cassava peroxidases was carried out using chromatofocusing column chromatography (CF) and isoelectric focusing gel eletrophoresis(IEF). By CF, cassava peroxidases were separated into 2 forms, the unbound and the bound forms. By IEF, the unbound form showed a pI valve of 6.8 and the bound form showed a pI valve of 3.5. By ND, the unbound form was found to be the positively charged isozyme and the bound form was the neutral isozyme. After storage for 7 days, the isozyme with pI valve of 6.8 increased but the isozyme with pI valve of 3.5 decreased in both cortex and parenchyma. The data suggested that the peroxidase isozyme with pI 6.8may play an important role in the physiological deterioration of cassava roots.
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