Squalene-hopene cyclase
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Squalene-hopene cyclase (SHC) (EC 5.4.99.17) or hopan-22-ol hydro-lyase is an enzyme in the terpene cyclase/mutase family. It catalyzes the interconversion of squalene into a pentacyclic triterpenes, hopene and hopanol.[2][3][4][5][6] This enzyme catalyses the following chemical reactions.
- squalene hop-22(29)-ene
- squalene + H2O hopan-22-ol
Squalene-hopene cyclase | |||||||||
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Identifiers | |||||||||
EC no. | 5.4.99.17 | ||||||||
CAS no. | 76600-69-6 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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SHC is important because its products, hopanoids, are very much like sterols in eukaryotes in that they condense lipid membranes and reduce permeability. In fact, SHC and sterol-producing enzymes (oxidosqualene cyclase) are evolutionarily related to each other.[7] Hopanoids are inferred to provide stability in the face of high temperatures and extreme acidity due to the rigid ring structure.[8] Indeed, up-regulation of SHC occurs in certain bacteria in the presence of hot or acidic environments.[9][10] SHC is found mostly in bacteria, but some eukaryotes, such as fungi and land plants, are also known to possess the enzyme.