Squalene/phytoene synthase family (original) (raw)

The squalene/phytoene synthase family represents proteins that catalyze the head-to-head condensation of C15 and C20 prenyl units (i.e. farnesyl diphosphate and genranylgeranyl diphosphate). This enzymatic step constitutes part of steroid and carotenoid biosynthesis pathway. Squalene synthase EC (SQS) and Phytoene synthase EC (PSY) are two well-known examples of this protein family and share a number of functional similarities. These similarities are also reflected in their primary structure. In particular three well conserved regions are shared by SQS and PSY; they could be involved in substrate binding and/or the catalytic mechanism. SQS catalyzes the conversion of two molecules of farnesyl diphosphate (FPP) into squalene. It is the first committed step in the cholesterol biosynthetic pa