[16] Eukaryotic prenyltransferases

摘要: Publisher Summary This chapter discusses the prenyltransferase of sterol biosynthesis in eukaryotes. enzyme condenses either a C 5 or 10 allylic pyrophosphate with homoallylic to give, as ultimate product, farnesyl which then serves substrate for squalene and synthesis. All eukaryotic synthetases are dimeric proteins molecular weight about 80,000. The specific activities homogeneous prenyltransferases vary from 900 pig liver 5200 yeast. There many different that produce every size product dimer (geranyl pyrophosphate) high polymers, gutta percha, rubber. Cis well trans isomers may be produced. these enzymes accept geranyl dimethylallylpyrophosphate substrates, Michaelis constants between 0.1 1 μM all substrates. It is also possible this produces dolichyl nonaprenyl (ubiquinone) However, it not clear if other participate those pathways. Prenyltransferase has been assayed onset by measuring conversion acid-stable (isopentenyl bearing radiolabel) acid-labile product. minor variations procedure, but general, after incubation mineral acid used hydrolysis nonpolar products thus formed extracted into an organic solvent determination radioactivity.