Transferases;
Transferring alkyl or aryl groups, other than methyl groups;
Transferring alkyl or aryl groups, other than methyl groups (only sub-subclass identified to date)
BRITE hierarchy

(2E,6E)-farnesyl-diphosphate:(2E,6E)-farnesyl-diphosphate farnesyltransferase

2 (2E,6E)-farnesyl diphosphate + NAD(P)H + H+ = squalene + 2 diphosphate + NAD(P)+ (overall reaction) [RN:R06223];
(1a) 2 (2E,6E)-farnesyl diphosphate = diphosphate + presqualene diphosphate [RN:R00702];
(1b) presqualene diphosphate + NAD(P)H + H+ = squalene + diphosphate + NAD(P)+ [RN:R02872]

R00702 R02872 R06223
Reaction

(2E,6E)-farnesyl diphosphate [CPD:C00448];
NADH [CPD:C00004];
NADPH [CPD:C00005];
H+ [CPD:C00080];
presqualene diphosphate [CPD:C03428]

This microsomal enzyme catalyses the first committed step in the biosynthesis of sterols. The enzyme from yeast requires either Mg2+ or Mn2+ for activity. In the absence of NAD(P)H, presqualene diphosphate (PSPP) is accumulated. When NAD(P)H is present, presqualene diphosphate does not dissociate from the enzyme during the synthesis of squalene from farnesyl diphosphate (FPP) [8]. High concentrations of FPP inhibit the production of squalene but not of PSPP [8].

EC 2.5.1.21 created 1976, modified 2005, modified 2012