Superoxide dismutase (SOD) is an important member of the antioxidant enzyme system in biological systems and is widely distributed in microorganisms, plants and animals.

According to the different metal prosthetic groups in SOD, SOD can be roughly divided into three categories, namely Cu/Zn-SOD, Mn-SOD, and Fe-SOD.

1. Cu/Zn-SOD: It is blue-green in color and mainly exists in the cytoplasm of eukaryotic cells. It is considered to exist in relatively primitive biological groups and is the most widely distributed.

2. Mn-SOD: pink in color, mainly found in the mitochondria of prokaryotes and eukaryotes.

3. Fe-SOD: yellow-brown in color, mainly found in prokaryotic cells. They can effectively scavenge superoxide anion free radicals (which carry an unpaired electron and a negative charge) to avoid excessive damage to cells. They have antioxidant, anti-radiation and anti-aging functions.

Distribution

1. Cu/Zn-SOD is present in most primitive invertebrate cells, while vertebrates generally contain Cu/Zn-SOD and Mn-SOD. Cu/Zn-SOD is contained in red blood cells and liver cells of humans, mice, pigs, cattle, etc., and it mainly exists in the cytoplasm, and also exists between the inner and outer membranes of mitochondria. Mn-SOD has also been purified from human and animal liver cells, and it generally exists in the mitochondrial matrix.

2. Fe-SOD in plant cells mainly exists in chloroplasts.

3. Fungi generally contain Mn-SOD and Cu/Zn-SOD. Most eukaryotic algae have Fe-SOD in their chloroplast matrix and Mn-SOD bound to the thylakoid membrane, while most algae do not contain Cu/Zn-SOD.