The following enzymes catalyze mechanistically related reactions which involve
the highly complex cyclic rearrangement of squalene or its 2,3 oxide:
Lanosterol synthase (EC 5.4.99.7) (oxidosqualene--lanosterol cyclase),
which catalyzes 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), a plant enzyme that catalyzes the cyclization of (S)-2,3-
epoxysqualene to cycloartenol.
Hopene synthase (EC 5.4.99.17) (squalene--hopene cyclase), a bacterial
enzyme that catalyzes the cyclization of squalene into hopene, a key step
in hopanoid (triterpenoid) metabolism.
These enzymes are evolutionary related [1] proteins of about 70 to 85 Kd. As a
signature pattern, we selected a highly conserved region which is rich in
aromatic residues and which is located in the C-terminal section.
PROSITE method (with tools and information) covered by this documentation:
Reference
1
Authors
Corey E.J. Matsuda S.P.T. Bartel B.
Title
Isolation of an Arabidopsis thaliana gene encoding cycloartenol synthase by functional expression in a yeast mutant lacking lanosterol synthase by the use of a chromatographic screen.
Source
Proc. Natl. Acad. Sci. U.S.A. 90:11628-11632(1993).
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