Superoxide dismutase

Superoxide dismutase
Model of the dimer of human cytoplasmic SOD according to PDB 2C9U
Identifier
External IDs	CAS number : 9054-89-1
Enzyme classification
EC, category	1.15.1.1 ,  oxidoreductase
Response type	Disproportionation
Substrate	2 O 2 • - + 2 H +
Products	O 2 + H 2 O 2

Superoxide dismutase (SOD) is the name for all enzymes that superoxide - anions to hydrogen peroxide to convert. These enzymes are found in all living things. Only a few anaerobic bacteria lack these enzymes. Superoxide (a reactive oxygen species ) is very reactive and can damage proteins and the genome ( oxidative stress ). The catalyzed reaction is therefore particularly important for aerobic organisms.

Systematics

There are three easily distinguishable groups of superoxide dismutases.

• SOD containing copper / zinc : a form found in the cytoplasm of all eukaryotes ; another form in plant chloroplasts ; an extracellular form in some eukaryotes; and a periplasmic form in prokaryotes . For example, the Cu, Zn-SOD of Mycobacterium tuberculosis is decisive for the defense against the immune response of infected macrophages.
• Manganese superoxide dismutases : Manganese - or SOD containing iron , in all living things. The iron-containing ones are localized in plants in the chloroplasts , the manganese- containing ones in mitochondria and peroxisomes . SODs are known from Bacteroides gingivalis and Streptococcus mutans , in which the metal ion Fe / Mn is freely exchangeable.
• Superoxide dismutases from the germin family ( glycoprotein family first discovered during plant germination) in the extracellular matrix of many plants.

Catalyzed reaction

The oxidized form of the enzyme reacts with a superoxide ion to form oxygen and the reduced form of the enzyme. This form further reacts with a second superoxide ion and two protons , producing hydrogen peroxide and the oxidized form of the enzyme.

${\displaystyle \mathrm {2O_{2}^{-}+2H^{+}\longrightarrow H_{2}O_{2}+O_{2}} }$

Two molecules of the hydrogen peroxide thus formed react further to form one molecule of oxygen and two molecules of water. This reaction is catalyzed by the enzyme catalase .

pathology

Recent research suggests that defects in an SOD gene (SOD1) in humans can lead to the hereditary disease of the familial form of amyotrophic lateral sclerosis (fALS). However, this effect has nothing to do with the enzyme property of SOD, but with the cytotoxic effects of unstabilized SOD. That mutation leads to an increased tendency of the protein to accumulate , which kills the cells, similar to the accumulation of β-amyloid in Alzheimer's disease .

Individual evidence

1. ↑ PROSITE PDOC00082
2. ↑ PDOC00083
3. ↑ PDOC00597
4. ↑ Alscher RG et al .: Role of superoxide dismutases (SODs) in controlling oxidative stress in plants. J Exp Bot 53/372/ 2002 . Pp. 1331-41. PMID 11997379
5. ↑ Piddington DL, Fang FC, Laessig T, Cooper AM, Orme IM, Buchmeier NA: Cu, Zn superoxide dismutase of Mycobacterium tuberculosis contributes to survival in activated macrophages that are generating an oxidative burst . In: Infection and Immunity . 69, No. 8, August 2001, pp. 4980-7. doi : 10.1128 / IAI.69.8.4980-4987.2001 . PMID 11447176 . PMC 98590 (free full text).
6. ↑ Amano A, Shizukuishi S, Tamagawa H, Iwakura K, Tsunasawa S, Tsunemitsu A: Characterization of superoxide dismutases purified from either anaerobically maintained or aerated Bacteroides gingivalis . In: J. Bacteriol. . 172, No. 3, March 1990, pp. 1457-63. PMID 2307656 . PMC 208620 (free full text).
7. ↑ Martin ME, Byers BR, Olson MO, Salin ML, Arceneaux JE, Tolbert C: A Streptococcus mutans superoxide dismutase that is active with either manganese or iron as a cofactor . In: J. Biol. Chem. . 261, No. 20, July 1986, pp. 9361-7. PMID 3722201 .
8. ↑ OMIM : 147450
9. ↑ UniProt entry
10. ↑ Furukawa Y. et al .: Complete loss of post-translational modifications triggers fibrillar aggregation of SOD1 in familial form of ALS. J. Biol. Chem. 283/35/ 2008 S. 24,167 to 24,176. PMID 18552350 - doi : 10.1074 / jbc.M802083200
11. ↑ L. Banci et al .: SOD1 and amyotrophic lateral sclerosis: mutations and oligomerization. PLoS ONE 3 / - / 2008 p. E1677-E1677. PMID 18301754 - doi : 10.1371 / journal.pone.0001677