PRODUCTS OF SACCHAROMYCES-CEREVISIAE CIS-PRENYLTRANSFERASE ACTIVITY IN-VITRO

Products of cis-prenyltransferase activity, the first committed enzyme of the dolichol biosynthetic pathway, have been characterized in Sacc haromyces cerevisiae. The evidence based on the results of ion exchang e, HPTLC chromatography and acid phosphatase digestion has been presen ted indicating that the final product of the enzyme action in vitro is free polyprenol and not polyprenol mono- or diphosphate. On the other hand, the results of HPLC analysis confirmed that in vivo yeast accum ulate alpha-saturated polyprenols (dolichols). Phosphorylation of endo genous dolichols by cytidine triphosphate (CTP)-dependent kinase is de monstrated. The hypothesis is put forth that in S cerevisiae free poly prenol is the substrate for the alpha-reductase responsible for its co nversion to dolichol which in turn is phosphorylated into its active f orm: dolichyl phosphate.