On the Stability of Bovine Superoxide Dismutase
نویسنده
چکیده
1. Apo-superoxide dismutase was more labile toward a variety of inactivating stresses than was the holoenzyme. 2. cu++ restored catalytic activity to the apoenzyme and markedly enhanced its thermal stability but Cu++ plus Zn++ were needed to attain the stability of the native enzyme. 3. Co’-+ or Hgii were able to replace Zn++ in increasing the thermal stability of the Cu+f-repleted apoenzyme. Indeed, the enzyme containing Hg++ + Cu++ was more stable than the native superoxide dismutase. In contrast no metal was found which could replace Cu++ in restoring activity to the apoenzyme. 4. Arrhenius plots showed that rates of irreversible inactivation were a biphasic function of temperature in the case of apo-superoxide dismutase but were monophasic in the presence of those metals which aBected thermal stability. Metal binding apparently changed the pathway of thermal inactivation. 5. Since excess Cu++ could not substitute for Cu++ + Zn++ and since excess Zni+ could not prevent the effect of Cu++ we conclude that the Cu++ site cannot bind Zn++ and the Zn++ site cannot bind Cu+f, although it can bind Co++ or Hg++. 6. Native superoxide dismutase retained much of its activity in the presence of 10.0 M urea or 4% sodium dodecyl sulfate and, although high concentrations of guanidinium chloride did inhibit, its effects were reversible by dialysis or dilution. 7. Guanidinium-chloride did however perturb the structure of the holoenzyme in a way which rendered its metals accessible to EDTA such that exposure to EDTA plus guanidinium chloride resulted in progressive inactivation. 8. It appears likely, on the basis of data available at present, that Zn++ plays a structural role in the bovine erythrocyte superoxide dismutase and lends it enhanced stability whereas Cu++ is directly involved in the catalytic cycle.
منابع مشابه
Modeling, Mutagenesis and In-silico Structural Stability Assay of the Model of Superoxide Dismutase of Lactococcus Lactis Subsp. Cremoris MG1363
Background:Characterizing the structure and function of superoxide dismutase (SOD), as an antioxidant enzyme providing opportunities for its application in food supplements. Objectives: In this study, the features of the Manganese-SOD of Lactococcus lactis (SDLL), subsp. cremoris MG1363, as probiotic bacteria, were determined on the ...
متن کاملContribution of conformational stability and reversibility of unfolding to the increased thermostability of human and bovine superoxide dismutase mutated at free cysteines.
The conformational stability and reversibility of unfolding of the human dimeric enzyme Cu Zn superoxide dismutase (HSOD) and the three mutant enzymes constructed by replacement of Cys6 by Ala and Cys111 by Ser, singly and in combination, were determined by differential scanning calorimetry. The differential scanning calorimetry profile of wild-type HSOD consists of two components, which probab...
متن کاملSequence homologies among bacterial and mitochondrial superoxide dismutases.
Superoxide dismutase from chicken-liver mitochondria (manganese enzyme) and the two dismutases from Escherichia coli (manganese and iron enzymes) were analyzed through 29 cycles of automated Edman degradations. The high degree of homology among the amino-terminal sequences of these three dismutases corroborates their known similarity of structural and functional properties, and serves as furthe...
متن کاملEffects of 1-MCP and Ethylene on Antioxidant Enzymes Activity and Postharvest Physio-Biochemical Characteristics of Cut Carnation Flower cv. ‘Fortune’
Carnation (Dianthus caryophyllus L.) is one of the most important cut flowers in the world. Themajority of thecarnation cultivars are sensitive to ethylene which affected the physiological and biochemical postharvest characteristics of these flowers.Applying inhibitors of biosynthesis and action of ethylene is important factor to protect the display quality and extend postharvest life. In order...
متن کامل