Delta(24)-sterol reductase; Catalyzes the reduction of the delta-24 double bond of sterol intermediates during cholesterol biosynthesis. In addition to its cholesterol-synthesizing activity, can protects cells from oxidative stress by reducing caspase 3 activity during apoptosis induced by oxidative stress. Also protects against amyloid-beta peptide-induced apoptosis (By similarity).

Squalene monooxygenase; Catalyzes the stereospecific oxidation of squalene to (S)- 2,3-epoxysqualene, and is considered to be a rate-limiting enzyme in steroid biosynthesis.

Lanosterol 14-alpha demethylase; A cytochrome P450 monooxygenase involved in sterol biosynthesis. Catalyzes 14-alpha demethylation of lanosterol and 24,25- dihydrolanosterol likely through sequential oxidative conversion of 14- alpha methyl group to hydroxymethyl, then to carboxylaldehyde, followed by the formation of the delta 14,15 double bond in the sterol core and concomitant release of formic acid. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P45 [...]

Sterol-4-alpha-carboxylate 3-dehydrogenase, decarboxylating; Involved in the sequential removal of two C-4 methyl groups in post-squalene cholesterol biosynthesis.

3-keto-steroid reductase; Responsible for the reduction of the keto group on the C-3 of sterols; Belongs to the short-chain dehydrogenases/reductases (SDR) family. ERG27 subfamily.

Lanosterol synthase; Catalyzes the cyclization of (S)-2,3 oxidosqualene to lanosterol, a reaction that forms the sterol nucleus. Through the production of lanosterol may regulate lens protein aggregation and increase transparency.

Cholesterol 25-hydroxylase; Catalyzes the formation of 25-hydroxycholesterol from cholesterol, leading to repress cholesterol biosynthetic enzymes. Plays a key role in cell positioning and movement in lymphoid tissues: 25-hydroxycholesterol is an intermediate in biosynthesis of 7-alpha,25-dihydroxycholesterol (7-alpha,25-OHC), an oxysterol that acts as a ligand for the G protein-coupled receptor GPR183/EBI2, a chemotactic receptor for a number of lymphoid cells. May play an important role in regulating lipid metabolism by synthesizing a corepressor that blocks sterol regulatory element [...]

Sterol O-acyltransferase 1; Catalyzes the formation of fatty acid-cholesterol esters, which are less soluble in membranes than cholesterol. Plays a role in lipoprotein assembly and dietary cholesterol absorption; Belongs to the membrane-bound acyltransferase family. Sterol o-acyltransferase subfamily.

Sterol O-acyltransferase 2; Plays a role in lipoprotein assembly and dietary cholesterol absorption. In addition to its acyltransferase activity, it may act as a ligase. May provide cholesteryl esters for lipoprotein secretion from hepatocytes and intestinal mucosa; Belongs to the membrane-bound acyltransferase family. Sterol o-acyltransferase subfamily.