68 by: Shahirah Bagnee
Student – Shahirah Bagnee
Name of enzyme and E.C. number – Superoxide dismutase (SOD); EC 1.15.1.1
Where is enzyme found? Superoxide dismutase is present in all eukaryotes and some prokaryotes and there are 3 main classes of SOD with distinct protein folds and different catalytic metal ions. We have SOD1, found in the cytosol and SOD3 found in extracellular fluids. They use a Zinc ion to stabilise a histidine residue on the SOD molecule and Copper ion for the catalysis reaction. We also have SOD2 which is present in the mitochondria, and they use Manganese ion(Mn) for catalysis.
What does the enzyme do? To learn about what the enzyme SOD does we need to understand what superoxide is. Superoxide(O2.-) is a free radical and is generated by several biological processes in an organism such as during aerobic metabolism, in oxidative phosphorylation, in photosynthesis and during an immune response by activated macrophages and neutrophils. It is related to toxicity and may result in inflammation as well as cell injury related to DNA damage. That cellular damage in turn is implicated in many diseased such as cancer, cardiovascular disease and has a major effect on aging. SOD therefore is an enzyme that rapidly decomposes the superoxide anion radicals into molecular oxygen and hydrogen peroxide hence it controls cellular oxygen reactive species (ORS) levels. The hydrogen peroxide which is also toxic will get broken down by catalase enzymes. SOD disproportionate the superoxide radical by alternate reduction and oxidation of catalytic metal ions (e.g Cu2+). The active sites of the SOD has water and metal ions that help in the reaction. In all SOD acts as an antioxidant enzyme that scavenges oxygen radicals through oxidation/reduction cycles at a very high reaction rate through transition metal ions present at the active site. SOD requires those cofactors such as manganese, iron, copper or zinc for maximum catalytic activity.
Any other interesting facts or important information on your enzyme:
- – The mechanism of superoxide dismutase(SOD) is quite unique since its mechanism is purely inorganic which means there are no Carbons involved in the reaction. It does not act on any substrate that contains Carbon. SOD is acting on Hydrogens, Oxygens and Metal ions (such as Cu and Zn).
- – SOD expression can suppress the malignant phenotype of human melanoma cells.
- – SOD is being researched as a potential therapeutic agent in conditions characterized by oxidative stress.
- – SOD structures may also control their enzymatic activity through product inhibition
References
a) Perry JJP, Shin DS, Getzoff ED, Tainer JA. 2010. The structural biochemistry of the superoxide dismutases. Biochimica et Biophysica Acta (BBA) – Proteins and Proteomics. 1804(2):245–262. doi:https://doi.org/10.1016/j.bbapap.2009.11.004.
b) “Superoxides and Superoxide Dismutase: Physiology, Biochemistry, and Inorganic Mechanism.” Www.youtube.com, www.youtube.com/watch?v=8doesahSy4w. Accessed 29 May 2021.
c) Zheng, Mengli, et al. “The Applications and Mechanisms of Superoxide Dismutase in Medicine, Food, and Cosmetics.” Antioxidants, vol. 12, no. 9, 1 Sept. 2023, p. 1675, www.mdpi.com/2076-3921/12/9/1675#:~:text=SODs%20Catalyze%20the%20Reaction%20and, https://doi.org/10.3390/antiox12091675.
