Squalene synthase (SQS) (SS) (EC 2.5.1.21) (FPP:FPP farnesyltransferase) (Farnesyl-diphosphate farnesyltransferase) (Farnesyl-diphosphate farnesyltransferase 1)
1_MEFVK 6_ CLGHP 11_ EEFYN 16_ LVRFR 21_ IGGKR 26_ KVMPK 31_ MDQDS 36_ LSSSL 41_ KTCYK 46_ YLNQT 51_ SRSFA 56_ AVIQA 61_ LDGEM 66_ RNAVC 71_ IFYLV 76_ LRALD 81_ TLEDD 86_ MTISV 91_ EKKVP 96_ LLHNF 101_ HSFLY 106_ QPDWR 111_ FMESK 116_ EKDRQ 121_ VLEDF 126_ PTISL 131_ EFRNL 136_ AEKYQ 141_ TVIAD 146_ ICRRM 151_ GIGMA 156_ EFLDK 161_ HVTSE 166_ QEWDK 171_ YCHYV 176_ AGLVG 181_ IGLSR 186_ LFSAS 191_ EFEDP 196_ LVGED 201_ TERAN 206_ SMGLF 211_ LQKTN 216_ IIRDY 221_ LEDQQ 226_ GGREF 231_ WPQEV 236_ WSRYV 241_ KKLGD 246_ FAKPE 251_ NIDLA 256_ VQCLN 261_ ELITN 266_ ALHHI 271_ PDVIT 276_ YLSRL 281_ RNQSV 286_ FNFCA 291_ IPQVM 296_ AIATL 301_ AACYN 306_ NQQVF 311_ KGAVK 316_ IRKGQ 321_ AVTLM 326_ MDATN 331_ MPAVK 336_ AIIYQ 341_ YMEEI 346_ YHRIP 351_ DSDPS 356_ SSKTR 361_ QIIST 366_ IRTQN 371_ LPNCQ 376_ LISRS 381_ HYSPI 386_ YLSFV 391_ MLLAA 396_ LSWQY 401_ LTTLS 406_ QVTED 411_YVQTG
1: Catalyzes the condensation of 2 farnesyl pyrophosphate (FPP) moieties to form squalene. Proceeds in two distinct steps. In the first half-reaction, two molecules of FPP react to form the stable presqualene diphosphate intermediate (PSQPP), with concomitant release of a proton and a molecule of inorganic diphosphate. In the second half-reaction, PSQPP undergoes heterolysis, isomerization, and reduction with NADPH or NADH to form squalene. It is the first committed enzyme of the sterol biosynthesis pathway