The biosynthesis of triterpenoid carotenoids in Streptococcus faecium UNH 564P.

Abstract

Cell-free enzyme preparations from Streptococcus faecium UNH 564P and Phycomyces blakesleeanus strain C5-car10(-) were used to study the incorporation of [14C]isopentenyl pyrophosphate and either all-trans-[4,8,12-3H]farnesyl pyrophosphate (FPP) or all-trans--[4,8,12,16-3H]geranylgeranyl pyrophosphate (GGPP) into squalene and the carotenoids of the organisms. It was found that the triterpenoid (C30) carotenoids of S. faecium are formed by condensation of two molecules of FPP similar to squalene biosynthesis rather than by condensation of two molecules of GGPP with subsequent degradation. Additional studies have shown that carotenoid glucoside biosynthesis in S. faecium extracts is stimulated by the addition of glucose and UDP-glucose. Such glucoside biosynthesis appears maximal in systems exposed to aeration. These results confirm that the triterpenoid carotenoids in S. faecium are symmetrical and are representatives of a unique new class of carotenoids.