Interplay between the cis-prenyltransferases and polyprenol reductase in the yeast Saccharomyces cerevisiae.

Dolichol formation is examined in three Saccharomyces cerevisiae strains with mutations in the ERG20 gene encoding farnesyl diphosphate synthase (mevalonic acid pathway) and/or the ERG9 gene encoding squalene synthase (sterol synthesis pathway) differing in the amount and chain length of the polyisoprenoids synthesized. Our results suggest that the activities of two yeast cis-prenyltransferases Rer2p and Srt1p and polyprenol reductase are not co-regulated and that reductase may be the rate-limiting enzyme in dolichol synthesis if the amount of polyisoprenoids synthesized exceeds a certain level. We demonstrate that reductase preferentially acts on typical polyprenols with 13-18 isoprene residues but can reduce much longer polyprenols with even 32 isoprene residues.