ENTRY       EC 2.5.1.21
NAME        Farnesyl-diphosphate farnesyltransferase
            Farnesyltransferase
            Presqualene-diphosphate synthase
            Squalene synthetase
CLASS       Transferases
            Transferring alkyl or aryl groups, other than methyl groups
SYSNAME     Farnesyl-diphosphate:farnesyl-diphosphate farnesyltransferase
REACTION    2 Farnesyl diphosphate = Pyrophosphate +
            Presqualene diphosphate;
            Presqualene diphosphate = Pyrophosphate +
            Cyclopropylcarbinyl cation;
            Cyclopropylcarbinyl cation + NADPH = Squalene + NADP+
SUBSTRATE   Farnesyl diphosphate
            Presqualene diphosphate
            NADPH
            Cyclopropylcarbinyl cation
PRODUCT     Pyrophosphate
            Presqualene diphosphate
            Cyclopropylcarbinyl cation
            NADP+
            Squalene
INHIBITOR   alpha-Phosphono sulfonate triacid
COMMENT     The polymeric form of the enzyme also catalyses the reduction of
            presqualene diphosphate by NADPH to squalene via cationic 
            intermediate, cyclopropylcarbinyl cation, which was trapped as
            the corresponding alcohol, rillingol, by using a dihydro analog of 
            NADPH as the reducing agent (J.Am.Chem.Sco., 118, 13089 (1996)).
PATHWAY     PATH: MAP00100  Sterol biosynthesis
            PATH: MAP00900  Terpenoid biosynthesis
DISEASE     MIM: 184420  Farnesyl-diphosphate farnesyltransferase 1
MOTIF       PS: PS01044  Y-[CSA]-x(2)-V-A-[GA]-x-V-G
            PS: PS01045  [LIVM]-G-x(3)-Q-x(2)-N-I-x-R-D-[LIVMFY]-x(2)-[DE]-x(4)-
                         R-x-[FY]-x-P
GENES       SCE: YHR190W(ERG9)
            HSA: FDFT1
DBLINKS     University of Geneva ENZYME DATA BANK: 2.5.1.21
            WIT (What Is There) Metabolic Reconstruction: 2.5.1.21
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