High-level expression of a sika deer (Cervus nippon) Cu/Zn superoxide dismutase in Pichia pastoris and its characterization

Characterization of a Novel Superoxide Dismutase from a Deep-sea Sea Cucumber (Psychoropotes verruciaudatus)

At present, deep-sea enzymes are a research hotspot. In this study, a novel copper-zinc superoxide dismutase (CuZnSOD) was successfully cloned and characterized from a new species of sea cucumber Psychropotes verruciaudatus (PVCuZnSOD). The relative molecular weight of the PVCuZnSOD monomer is 15 kDa. The optimum temperature of PVCuZnSOD is 20 °C, and it maintains high activity in the range of 0-60 °C. It also has high thermal stability when incubated at 37 °C. PVCuZnSOD has a maximum activity of more than 50% in the pH range of 4-11 and a high activity at pH 11. In addition, PVCuZnSOD has strong tolerance to Ni²⁺, Mg²⁺, Ba²⁺, and Ca²⁺, and it can withstand chemical reagents, such as Tween20, TritonX-100, ethanol, glycerol, isopropanol, DMSO, urea, and GuHCl. PVCuZnSOD also shows great stability to gastrointestinal fluid compared with bovine SOD. These characteristics show that PVCuZnSOD has great application potential in medicine, food, and other products.

Preparation and Characterization of pH-Sensitive Capsosomes for Oral Delivery of Therapeutic Proteins

Oral administration of therapeutic proteins is very challenging because of gastrointestinal instability and decomposition. In this study, we developed a system for oral delivery of superoxide dismutase (SOD) as one of the therapeutic proteins. SOD-loaded capsosomes (SOD-C) were formed by the assembly of chitosan-coated solid lipid nanoparticles and SOD-loaded liposomes (SOD-L). Unlike raw SOD activity decreases to 19.41% in SGF and 13.70% in SIF, the SOD-C in SGF (89.30%) condition retained its initial catalytic activity and decreased but exhibited a three-fold higher raw SOD activity even after incubation in SIF (41.63%). TEM analysis indicated that after intestinal digestion, the residual amount of intact liposomes affected the higher catalytic activity of SOD-C compared to raw SOD and SOD-L. Based on these results, significantly higher cellular uptake of SOD-C was observed compared to raw SOD. Also, SOD-C remarkably suppressed the cellular malondialdehyde (MDA) concentration by maintaining the antioxidative capacity of SOD to remove MDA produced in the oxidative stress-induced cells, thereby contributing to a significant five-fold difference with SOD-R (p < 0.05). This delivery system can facilitate the oral application of other therapeutic proteins, improving gastrointestinal stability.

Complete Amino Acid Sequence of a Copper/Zinc-Superoxide Dismutase from Ginger Rhizome

Superoxide dismutase (SOD) is an antioxidant enzyme protecting cells from oxidative stress. Ginger (Zingiber officinale) is known for its antioxidant properties, however, there are no data on SODs from ginger rhizomes. In this study, we purified SOD from the rhizome of Z. officinale (Zo-SOD) and determined its complete amino acid sequence using N terminal sequencing, amino acid analysis, and de novo sequencing by tandem mass spectrometry. Zo-SOD consists of 151 amino acids with two signature Cu/Zn-SOD motifs and has high similarity to other plant Cu/Zn-SODs. Multiple sequence alignment showed that Cu/Zn-binding residues and cysteines forming a disulfide bond, which are highly conserved in Cu/Zn-SODs, are also present in Zo-SOD. Phylogenetic analysis revealed that plant Cu/Zn-SODs clustered into distinct chloroplastic, cytoplasmic, and intermediate groups. Among them, only chloroplastic enzymes carried amino acid substitutions in the region functionally important for enzymatic activity, suggesting that chloroplastic SODs may have a function distinct from those of SODs localized in other subcellular compartments. The nucleotide sequence of the Zo-SOD coding region was obtained by reverse-translation, and the gene was synthesized, cloned, and expressed. The recombinant Zo-SOD demonstrated pH stability in the range of 5-10, which is similar to other reported Cu/Zn-SODs, and thermal stability in the range of 10-60 °C, which is higher than that for most plant Cu/Zn-SODs but lower compared to the enzyme from a Z. officinale relative Curcuma aromatica.