Types of Reactions in Carotenogenesis

Carotenoids are usually tetraterpenoids consisting of eight isoprene units, Cj-compound. Four of the Cj units combine to yield a C o-compound, geranyl-geranyl pyrophosphate. In a tail-to-tail condensation of two these Cjq, the C40, phytoene, is formed by phytoene synthase (CrtB) whose reaction needs ATP 

Tabte 1. Carotenogenesis pathways and their distribution within anaerobic photosynthetic bacteria 

Normal spirilloxanthin Unusual spirilloxanthin Spirilloxanthin Unusual-Spirillo Rhodospirillaceae, Chromatiaceae, Ectothiorhodospiraceae Rhodospirillaceae, Chromatiaceae, Ectothiorhodospiraceae 4 

Erwinia iiredovora (Misawa et al., 1990) and Erwinia herbicola (Hundle et al., 1992). 

gehlinosiis (Ouchane et al., 1997a,b Igarashi et al., 1998 . V. P. Nagashima, personal communications). 

---