Kathryn M. McLellan

Superoxide dismutases in foods. A review

Abstract The importance of superoxide dismutase (SOD) in providing a defence against the superoxide radical in living systems has been increasingly established during the last twenty years. More recently, the occurrence and role of SOD in post-harvest and post-mortem foods and its significance as a natural antioxidant have been studied. This review highlights the importance of superoxide dismutase in foods. Current knowledge in aspects such as assay methods and the potential role of superoxide dismutase in the preservation of quality of harvested fruits and vegetables is reviewed.

The effect of heat on cabbage and Brussels sprout peroxidase enzymes

Abstract Preparations of soluble, ionically bound and covalently bound peroxidases extracted from cabbage and Brussels sprout have been obtained. The effect of heating each fraction at 60°C, 65°C, 70°C and 75°C on peroxidase activity has been studied. Biphasic inactivation kinetics were observed in all cases, except for Spring cabbage ionically bound peroxidases, which were also found to be less heat stable. Heat inactivation energies for the inactivation of the peroxidases in each fraction have been calculated. Following inactivation, incubation at 30°C allowed regeneration of some of the inactivated peroxidase enzymes in the case of each of the three soluble fractions, but only Brussels sprout ionically bound peroxidases showed detectable regeneration.

Purification and heat stability of Brussels sprout peroxidase isoenzymes

Abstract Using gel filtration and ion-exchange chromatography, a total of four peroxidase isoenzymes were isolated from extracts of Brussels sprouts. The isoenzymes were found to vary in their substrate specificities and heat stability properties. Three of the isoenzymes showed biphasic inactivation in response to heating, while the fourth isoenzyme was relatively heat labile and inactivated in a more linear manner with time. Regeneration following heat inactivation was not observed for the isolated isoenzymes.

The heat stability of purified spring cabbage peroxidase isoenzymes

Abstract Two peroxidase isoenzymes, purified from extracts of Spring cabbage, have been shown to possess different heat-stabilities. The anionic isoenzyme had an isoelectric point of 3·7 and was relatively heat stable, while the cationic isoenzyme, pI 9·9, was more readily inactivated by heat. Neither isoenzyme showed regeneration of peroxidase activity following heat inactivation.

Heat stability of peroxidases from orange

Abstract Soluble and ionically bound peroxidases have been obtained from orange juice and the albedo. A high level of peroxidase activity was present in the albedo. Non-linear heat inactivation was observed for orange peroxidases. The bound peroxidases were particularly heat stable and regenerated when held at 30°C following heat inactivation. A small amount of regeneration was observed for orange soluble peroxidases.

Heat stability of superoxide dismutase in cabbage

Abstract The occurrence of superoxide dismutase activity (SOD) in extracts of cabbage (Brassica oleracea var. capitata) was detected by use of the nitroblue tetrazolium assay method for the measurement of superoxide anion (O−2). The SOD activity found in aqueous extracts of cabbage was destroyed at temperatures greater than 45°C, whereas, for commercial preparations of bovine SOD, temperatures in excess of 65°C were required for deactivation of the enzyme. Heat inactivation energies have been calculated. Tests for sensitivity to cyanide have indicated that a substantial proportion of the cabbage SOD activity is due to the CuZn type of enzyme. As shown by isoelectric focusing, three SOD isoenzymes were present in the aqueous extracts of cabbage.

Cabbage and brussels sprout peroxidase isoenzymes separated by isoelectric focussing

Abstract Peroxidase isoenzymes have been detected in extracts obtained from Brassica oleracea var. capitata (cabbage), spring cabbage and Brassica oleracea var. gemmifera (Brussels sprouts) by use of the technique of isoelectric focussing. Soluble peroxidases were composed of both anionic and cationic enzymes. Peroxidases ionically bound to cell wall fragments were entirely of the cationic type. Isoenzyme profiles were also obtained for heat treated soluble extracts.

Isolation and purification of superoxide dismutase purified from Brussels sprouts (Brassica oleracea L. var. bullata sub var. gemmifera)

Abstract The isoenzymes from Brussels sprouts ( Brassica oleracea var. gemmifera ), were characterised as CuZn-SOD by molecular weight, metal ion content and inhibition by cyanide. Isoelectric focusing (IEF) showed Brussels sprouts superoxide dismutase to consist of three isoenzymes. The two major isoenzymes, pI 4·5 and 4·7, A and B of Brussels sprouts SOD were separated and shown to possess different thermal inactivation properties. A subunit (approx. MW 16 000) for isoenzyme B has been detected, whereas for isoenzyme A two possible subunits (MW 16 000 and 19 000) may have been detected. Isoenzyme A was more stable to heat than isoenzyme B.