Squalene synthase

Squalene synthase
	Existing structural data : 1EZF
Properties of human protein
Mass / length primary structure	417 amino acids
Secondary to quaternary structure	Monomer; multipass membrane protein (ER)
Cofactor	Mg 2+
Identifier
Gene name	FDFT1
External IDs	OMIM : 184420 ; UniProt : P37268 ;
Enzyme classification
EC, category	2.5.1.21 , transferase
Response type	Transfer of a farnesyl residue
Substrate	2 farnesyl diphosphate + 2 NADPH / H +
Products	Squalene + 2 PP i + 2 NADP +
Occurrence
Parent taxon	Eukaryotes

Squalene synthase (SQS) (also: farnesyl diphosphate farnesyl transferase, FDFT) is the enzyme that catalyzes the condensation reaction of two molecules of farnesyl diphosphate to squalene in eukaryotes . This is a sub-step in cholesterol biosynthesis and the first reaction that leads exclusively to cholesterol in animals. It is a transmembrane protein that is located on the endoplasmic reticulum . SQS is a promising pharmacological target for lowering cholesterol levels.

There are homologous enzymes in carotene- producing organisms that condense geranylgeranyl diphosphate (GGPP) to phytoene as part of this synthesis .

Catalyzed reaction

The reaction takes place in two sub-steps:

2 ⇔
⇔ + PP _i

First, two farnesyl diphosphate molecules condense to form prequalene diphosphate.

+ 2 NADPH / H ⁺ ⇔
⇔ + 2 NADP ⁺ + PP _i

Then presqualene diphosphate is reduced to squalene and rearranged.

↑ ^a ^b European Institute of Bioinformatics (EBI): InterPro IPR006449 Farnesyl-diphosphate farnesyltransferase. Retrieved August 15, 2011 .
↑ UniProt P37268
↑ Do R, Kiss RS, Gaudet D, Engert JC: Squalene synthase: a critical enzyme in the cholesterol biosynthesis pathway . In: Clin. Genet. . 75, No. 1, January 2009, pp. 19-29. doi : 10.1111 / j.1399-0004.2008.01099.x . PMID 19054015 .

Wikibooks: Biochemistry and Pathobiochemistry: Cholesterol Biosynthesis - Learning and Teaching Materials