Family

Squalene cyclase (IPR018333)

Short name: Squalene_cyclase

Overlapping homologous superfamilies

None.

Family relationships

Description

Several enzymes catalyse mechanistically related reactions which involve the highly complex cyclic rearrangement of squalene or its 2,3 oxide. Squalene cyclase (SQCY) and 2,3-oxidosqualene cyclase (OSQCY) are integral membrane proteins that catalyze a cationic cyclization cascade converting linear triterpenes to fused ring compounds [PMID: 11027983, PMID: 9295270]. Lanosterol synthase (EC:5.4.99.7) (oxidosqualene--lanosterol cyclase) catalyses the cyclization of (S)-2,3-epoxysqualene to lanosterol, the initial precursor of cholesterol, steroid hormones and vitamin D in vertebrates and of ergosterol in fungi (gene ERG7). Cycloartenol synthase (EC:5.4.99.8) (2,3-epoxysqualene--cycloartenol cyclase), is a plant enzyme that catalyzes the cyclization of (S)-2,3-epoxysqualene to cycloartenol [PMID: 9519404], and hopene synthase (EC:5.4.99) (squalene--hopene cyclase), is a bacterial enzyme that catalyzes the cyclization of squalene into hopene or diplopterol, a key step in hopanoid (triterpenoid) metabolism [PMID: 9931258, PMID: 2253626]. These enzymes are evolutionary related [PMID: 7505443] proteins of about 70 to 85 kDa and have an alpha 6 - alpha 6 barrel fold. Deletion of a single glycine residue of Alicyclobacillus acidocaldarius SQCY alters its substrate specificity into that of eukaryotic OSQCY [PMID: 15593147]. Both enzymes have a second minor domain, which forms an alpha-alpha barrel that is inserted into the major domain.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0016866 intramolecular transferase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
CDD
TIGRFAMs