Spheroidene pathway

Spirilloxanthin pathway (normal spirilloxanthin, unusual spirilloxanthin, spheroidene, and carotenal pathways). 

Fig. 5. The pathway for the biosynthesis of spheroidene including enzymes (see Table 2). The pathway from chloroxanthin to 3,4-dihydrospheroidene may not be involved in in vivo, and 3,4-dihydrospheroidene may not be changed to spheroidene.

The spheroidene pathway is found only from four genera, Rhodobacter, Rhodoferax, Rubrivivax and Rhodovulum, this includes 13 species of the Rhodospirillaceae, and from some species of aerobic... 

This spheroidene pathway is a variant of the unusual spirilloxanthin pathway as a result of the different properties of the phytoene desaturases (CrtI). 

Albrecht M, Ruther A and Sandmann G (1997) Purification and biochemical characterization of a hydroxyneurosporene desaturase involved in the biosynthetic pathway of the carotenoid spheroidene in Rhodobacter sphaeroides. J Bacteriol 179 7462-7467... 

Special isopiene rule, 2669 Specific doses, 2423 Specific symptrans, 2423 Spectral generalizatiSpectrophotometric methods, 2073 Sperm count, 2420, 2421 Spermidine, 1732 Spermine, 1732 Sperm production, 2418 Sphacelariaceae, 2900-2901 Sphacelariales, 2900-2901 Sphaerococcaceae, 2890 Sphaerococcus coronopifolius, 2890 Sphaerotrichia japonica (Sphaerotrichia divaricata), 2896 Spherisorb ODS2, 3393 Spheroidene, 3270, 3271 Spheromastigote, 845 Spinacea oleracea, 864 Spinacia oleracea, 3584 Spindle cell sarcoma 45, 992 Spinosin, 2163 Spiranoid 5-lactone, 3472 Spiranthera, 735 Spirilloxanthin, 3268, 3270, 3271 Spirilloxanthin pathways, 3268, 3270, 3271 Spirostanols, ilXl-ZXiO, il il, 3239,... 

In the presence of nicotine (7.5 mmol" ), Rps. spheroides accumulates neurosporene in place of the two main pigments. - On re-suspending cells which had been washed free from nicotine, neurosporene disappeared and the normal pigments were synthesized. Experiments with Rps. gelatinosa showed that the same pathway existed in this organism, and emphasized the precursor-product relationship between spheroidene (151) and spheroidenone (153). These observations, combined with the characterization of the previously undetected demethylspheroidene (154) from cultures of both species, provide strong direct support for the biosynthetic pathway just indicated. No 3,4-didehydro-derivative of neurosporene (155) was detected in nicotine-inhibited cells, which suggests that the insertion of the double bond at C-3 does not normally occur before the hydration of the double bond at C-1. 

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