Carotenoid biosynthesis in Rhodomicrobium vannielii. Experiments with nicotine and 2-(4-chlorophenylthio)triethylammonium chloride (CPTA).

Nicotine and 2-(4-chlorophenylthio)triethylammonium chloride (CPTA) each inhibit production of the normal carotenoids of Rhodomicrobium vannielii (Rhodospirillaceae), especially rhodopin, beta-carotene and spirillixanthin, and cause the accumulation of lycopene. The inhibition of hydration of the C-1,2 double bond as well as cyclization is in agreement with proposals that these two reactions involve similar mechanisms. After removal of nicotine, cells reincubated in buffer solution or in the presence of diphenylamine convert accumulated lycopene into rhodopin. Under other conditions rhodopis is synthesized, on removal of nicotine, not from accumulated lycopene but from early precursors. The pathway of rhodopin and spirilloxanthin biosynthesis in Rm. vannielii is discussed briefly, and the possible involvement of enzyme aggregates in carotenoid biosynthesis is considered.