Effect of nicotine on biosynthesis of C₅₀ carotenoids in Halobacterium cutirubrum

Abstract

The major carotenoids in pigmented extreme halophiles are the hydroxylated C50 red pigments bacterioruberin (major, 84%) and monoanhydrobacterioruberin (minor, 14%). When cells of Halobacterium cutirubrum were grown in the presence of nicotine they accumulated lycopene and bisanhydrobacterioruberin; maximal accumulation (80% lycopene, 20% bisanhydrobacterioruberin) occurred at 3mM nicotine. Removal of nicotine resulted in the reformation of monoanhydrobacterioruberin and bacterioruberin at the expense of lycopene and bisanhydrobacterioruberin. Thus nicotine does not inhibit the addition of the two extra isoprene units plus two hydroxyl groups (at C1 and C1') to a C40 carotenoid skeleton. It does, however, inhibit the hydration steps at C3'' and C3''' that convert bisanhydrobacterioruberin to monoanhydrobacterioruberin and finally bacterioruberin. These results support the view that the C50 carotenoids can be formed from a C40 carotene, lycopene.

Bacterioopsin-Mediated Regulation of Bacterioruberin Biosynthesis in Halobacterium salinarum

“…As a first step to examine this possibility, we sought to identify the enzyme that catalyzes the conversion of lycopene to the first bacterioruberin intermediate. On the basis of biochemical studies (21,22), this biosynthesis is proposed to proceed via a condensation reaction that adds two 5-carbon isoprene units to each end of the 40-carbon lycopene to generate the 50-carbon tetrahydrobisanhydrobacterioruberin. This reaction is similar to that for the formation of flavuxanthin in Corynebacterium glutamicum catalyzed by the lycopene elongase enzyme (19,20).…”

“…A simple explanation for the observed accumulation of bacterioruberins is that, when BO levels are high, bacterioruberin synthesis is inhibited, which increases the pool of lycopene available for retinal synthesis. On the basis of biochemical studies, the committed step in bacterioruberin synthesis is the addition of two 5-carbon dimethylall pyrophosphate (DMAPP) or isopentyl pyrophosphate (IPP) molecules to the 40-carbon lycopene to make the 50-carbon tetrahydrobisanhydrobacterioruberin (22,24). Although a possible mech- FIG.…”

“…For retinal synthesis, lycopene cyclizes to form ␤-carotene, which is cleaved to form the 20-carbon retinal cofactor (23,42). Alternatively, lycopene may be used as a precursor for bacterioruberins: tetrahydrobisanhydrobacterioruberin, bisanhydrobacterioruberin, and bacterioruberin (22,24). These 50-carbon carotenoids function to increase membrane rigidity (25) and provide protection against UV light (36).…”

The biochemical basis for structural diversity in the carotenoids of chlorophototrophic bacteria

“…1). Trans-phytoene is produced in some cases, but phytoene is usually formed as a 15-cis-isomer in bacteria and plants (Armstrong 1997;Gregonis and Rilling 1974;Kushwaha and Kates 1979;Chamovitz et al 1992), and in many cases both trans-phytoene and 15-cis-phytoene accumulate (Armstrong et al 1990;Frigaard et al 2004;Martinez-Ferez et al 1994;Neudert et al 1998). Non-enzymatic photoisomerization, which favors the trans-isomer, is likely responsible for the observed trans-phytoene in bacteria that otherwise produce 15-cis-phytoene (Maudinas et al 1974).…”

Identification of lipophilic bioproduct portfolio from bioreactor samples of extreme halophilic archaea with HPLC-MS/MS

“…The existence of seven geometric isomers of BR in the sample extracts can be supported by the fact that BR is synthesized from the lycopene [42]. Regarding their different molecular energies due to the position of the cis-bond in the conjugated chain, their stability is also different, and reported as:…”