ID 2.5.1.21 DE squalene synthase. AN farnesyl-diphosphate farnesyltransferase. AN farnesyltransferase. AN presqualene-diphosphate synthase. AN presqualene synthase. AN squalene synthetase. CA (1) 2 (2E,6E)-farnesyl diphosphate + H(+) + NADPH = 2 diphosphate + CA NADP(+) + squalene. CA (2) 2 (2E,6E)-farnesyl diphosphate + H(+) + NADH = 2 diphosphate + NAD(+) CA + squalene. CC -!- This microsomal enzyme catalyzes the first committed step in the CC biosynthesis of sterols. CC -!- In the absence of NAD(P)H, presqualene diphosphate (PSPP) is CC accumulated. CC -!- When NAD(P)H is present, presqualene diphosphate does not dissociate CC from the enzyme during the synthesis of squalene from farnesyl CC diphosphate (FPP). CC -!- High concentrations of FPP inhibit the production of squalene but not CC of PSPP. DR Q9SDW9, BSS_BOTBR ; A0A345BJQ0, CLZ20_COCLU; Q4WAG4, ERG9_ASPFU ; DR A0A1D8PI71, ERG9_CANAL ; P78589, ERG9_CANAX ; A0SJQ5, ERG9_GANLU ; DR V6RPN0, ERG9_GIBZE ; P36596, ERG9_SCHPO ; P29704, ERG9_YEAST ; DR P53799, FDFT1_ARATH; Q32KR6, FDFT_BOVIN ; Q9HGZ6, FDFT_CANGA ; DR O74165, FDFT_CYBJA ; Q54DR1, FDFT_DICDI ; Q752X9, FDFT_EREGS ; DR P37268, FDFT_HUMAN ; P53798, FDFT_MOUSE ; Q7S4Z6, FDFT_NEUCR ; DR P53800, FDFT_NICBE ; Q5R6U3, FDFT_PONAB ; Q02769, FDFT_RAT ; DR Q92459, FDFT_USTMA ; Q9Y753, FDFT_YARLI ; A0A142ZC57, LOS_BOTBR ; DR A0A144YEA5, LSS_BOTBR ; A0A3G1DJL2, MFR6_PHOSM ; D0VFU8, SLSS_SOLLC ; DR A0A1P7Y0A2, SQS10_PANGI; A0A1P7Y0D4, SQS11_PANGI; A0A1P7Y0A8, SQS12_PANGI; DR A0A1P7Y0D0, SQS13_PANGI; O48666, SQS1_PANGI ; C9E894, SQS2_PANGI ; DR D2K762, SQS3_PANGI ; A0A1P7Y0C9, SQS8_PANGI ; //