SUPEROXIDE DISMUTASE FROM ZIZYPHUS MAURITIANA LAMK.: CHARACTERIZATION AND STABILITY AS A FUNCTION OF TEMPERATURE AND pH
2011
Kumar, Sunil | Jain, Veena | MALHOTRA, SARLA P.
Superoxide dismutase (SOD) was partially purified from ber pulp of var. Umran and characterized for its physicochemical and kinetic parameters. Molecular weight of the enzyme was found to be 35.6 kDa with subunit molecular weight of 17.8 kDa as judged by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. The enzyme followed Michaelis–Menten kinetics for its substrates, nitroblue tetrazolium and riboflavin with respective Km values of 100 and 4.2 µM. It had pH optima of 7.8 and was stable up to 40C. Using central composite rotatable design of response surface methodology to study interactive effect of temperature and pH on SOD activity at a time, it was found that between temperature (50–67C) and pH (7.7–8.5) variables, certain combinations of temperature and pH might yield 100% residual activity of SOD. This interactive effect predicted various possible combinations of temperature and pH which can play important role while processing of various fruits and vegetables. PRACTICAL APPLICATIONS: In the present paper, in addition to the conventional characterization of superoxide dismutase (SOD), simultaneous interactive effect of two most important parameters viz. temperature and pH has also been experimented using central composite rotatable design of response surface methodology. This interactive effect predicted the residual enzyme activity at various possible combinations of temperature and pH. This information can be useful while processing various fruits and vegetables because in contrast to many of the plant enzymes which get inactivated above ambient temperature and at pH below and above certain specified pH, SOD can tolerate high temperatures and minimize load of superoxide anions during processing of fruits.
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