Cloning, Purification, and Characterization of Recombinant Human Extracellular Superoxide Dismutase in SF9 Insect Cells

Interchangeable utilization of metals: New perspectives on the impacts of metal ions employed in ancient and extant biomolecules

Metal ions provide considerable functionality across biological systems, and their utilization within biomolecules has adapted through changes in the chemical environment to maintain the activity they facilitate. While ancient earth's atmosphere was rich in iron and manganese and low in oxygen, periods of atmospheric oxygenation significantly altered the availability of certain metal ions, resulting in ion replacement within biomolecules. This adaptation mechanism has given rise to the phenomenon of metal cofactor interchangeability, whereby contemporary proteins and nucleic acids interact with multiple metal ions interchangeably, with different coordinated metals influencing biological activity, stability, and toxic potential. The ability of extant organisms to adapt to fluctuating metal availability remains relevant in a number of crucial biomolecules, including the superoxide dismutases of the antioxidant defense systems and ribonucleotide reductases. These well-studied and ancient enzymes illustrate the potential for metal interchangeability and adaptive utilization. More recently, the ribosome has also been demonstrated to exhibit interchangeable interactions with metal ions with impacts on function, stability, and stress adaptation. Using these and other examples, here we review the biological significance of interchangeable metal ions from a new angle that combines both biochemical and evolutionary viewpoints. The geochemical pressures and chemical properties that underlie biological metal utilization are discussed in the context of their impact on modern disease states and treatments.

Production of functional human CuZn-SOD and EC-SOD in bitransgenic cloned goat milk

Human copper/zinc superoxide dismutase (CuZn-SOD) and extracellular superoxide dismutase (EC-SOD) are two superoxide dismutases that scavenge reactive oxygen species (ROS). Their biological role of eliminating oxidative stress caused by excessive ROS levels in living organisms has been utilized in medical treatment, preventing skin photoaging and food preservation. In this study, we employed two sequences that encode human CuZn-SOD and EC-SOD, along with goat beta-casein 5' and 3' regulatory elements, to construct mammary gland-specific expression vectors. Bitransgenic goats were generated using somatic cell nuclear transfer (SCNT), which employed co-transfection to generate bitransgenic goat fetal fibroblast cells as donor cells, and the expression of human CuZn-SOD and EC-SOD and their biological activities were assayed in the milk. PCR and Southern blot analysis confirmed that the cloned goat harbors both hCuZn-SOD and hEC-SOD transgenes. rhCuZn-SOD and rhEC-SOD were expressed in the mammary glands of bitransgenic goat, as determined by western blotting. The expression levels were 100.14 ± 5.09 mg/L for rhCuZn-SOD and 279.10 ± 5.38 mg/L for rhEC-SOD, as determined using ELISA. A total superoxide dismutase assay with WST-8 indicates that the biological activity of rhCuZn-SOD and rhEC-SOD in goat milk is 1451 ± 136 U/mL. The results indicate that two expression vectors can simultaneously transfect goat fetal fibroblast cells as donor cells to produce transgenic goats by SCNT, and the CuZn-SOD and EC-SOD proteins secreted in the mammary glands showed biological activity. The present study thus describes an initial step in the production of recombinant human SODs that may potentially be used for therapeutic purposes.

Thermostable Fe/Mn superoxide dismutase from Bacillus licheniformis SPB-13 from thermal springs of Himalayan region: Purification, characterization and antioxidative potential

Superoxide dismutase (SOD; EC 1.15.1.1) is an enzyme that scavenges free radicals and increases the longevity. In this study, a thermostable superoxide dismutase (SOD) from Bacillus licheniformis SPB-13, from Himalayan region was purified to homogeneity using ion exchange chromatography (DEAE-Sepharose). The SDS and native PAGE analysis showed that SOD is composed of two subunits of 32 kDa each and total molecular mass of the enzyme was estimated as 68 kDa. The specific activity of enzyme was 3965.51 U/mg and was purified to 16.17 folds. The SOD showed maximum activity with 60 mM Tris-HCl buffer at pH 8.0 for 2 min of incubation. Enzyme along with FeCl₃ as metal ion remained active till 70 °C. After reaction variables optimization, enzyme activity increased from 3965.51 to 4015.72 U/mg. Kinetic analysis of SOD showed k_m of 1.4 mM of NADH and V_max of 10000 U/mg of protein. Turnover number (k_cat) and catalytic efficiency (k_cat/K_m) were found to be 11,333 s^-1 and 7092.2 s^-1·mM^-1 NADH. The activation energy (E_a) was calculated as 2.67 kJ·mol^-1. After typing, it was found to be a member of Fe/Mn SOD family with IC₅₀ value of 25 μg/ml, prevented the cell death at a concentration of 30 μg/ml and it increased the cell viability by 30%.

Zinc(II) ion promotes anti-inflammatory effects of rhSOD3 by increasing cellular association

Recently, we demonstrated that superoxide dismutase 3 (SOD3) is a strong candidate for biomedicine. Anti-oxidant function of SOD3 was accomplished without cell penetration, and it inhibited the inflammatory responses via non-enzymatic functions. SOD3 has the heparin binding domain associating cell surface. Interestingly, we found that Zn2＋ promotes transduction effects of recombinant human SOD3 (rhSOD3) by increasing uptake via the heparin binding domain (HBD). We demonstrated an uptake of rhSOD3 from media to cell lysate via HBD, resulting in an accumulation of rhSOD3 in the nucleus, which was promoted by the presence of Zn2＋. This resulted in increased inhibitory effects of rhSOD3 on NF-kB and STAT3 signals in the presence of Zn2＋, which shows elevated association of rhSOD3 into the cells. These results suggest that an optimized procedure can help to enhance the inflammatory efficacy of rhSOD3, as a novel biomedicine. [BMB Reports 2017; 50(2): 85-90].