Sterol evolution

Tricyclohexaprenol, a possible forerunner of sterols in the evolution of biomembranes, was synthesized by construction of the cyclic network in one step using cation-olefin tricyclization and subsequent stereocontroUed attachment of the Cio appendage to ring C. 

Rohmer, M., P. Bouvier, and G. Ourisson. 1979. Molecular evolution of biomembranes structural equivalents and phylogenetic precursors of sterols. Proc. Natl. Acad. Sci. USA 76 847-851. 

Ishida H, Kuruta Y, Gotoh O, Yamashita C, Yoshida Y, et al. 1999. Structure, evolution, and liver-specific expression of sterol 12alpha-hydroxylase P450 (CYP8B). J Biochem (Tokyo) 126 19-25. 

Paquot, C., and H. Kaller. Evolutions of the sterols and the triterpenoid alcohols during the ripening of the fruits of the olive tree. C R Acad Sci SerC 1976 282 1041. 

The major dietary lipids for humans are animal and plant triacylglycerols, sterols, and membrane phospholipids. The process of lipid metabolism fashions and degrades the lipid stores and produces the structural and functional lipids characteristic of individual tissues. For example, the evolution of a highly organized nervous system has depended on the natural selection of specific enzymes to synthesize and degrade (turn over) the lipids of the brain and central nervous system. 

Volkman, J. K. (2005) Sterols and other triterpenoids source specificity and evolution of bios5uithetic pathways. Org. Geochem. 36,139-59. 

The influence of plant sterols on the phase properties of phospholipid bilayers has been studied by differential scanning calorimetry and X-ray diffraction [206]. It is interesting that the phase transition of dipalmitoylglycerophosphocholine was eliminated by plant sterols at a concentration of about 33 mole%, as found for cholesterol in animal cell membranes. However, less effective modulation of lipid bilayer permeability by plant sterols as compared with cholesterol has been reported. The molecular evolution of biomembranes has received some consideration [207-209]. In his speculation on the evolution of sterols, Bloch [207] has suggested that in the prebiotic atmosphere chemical evolution of the sterol pathway if it did indeed occur, must have stopped at the stage of squalene because of lack of molecular oxygen, an obligatory electron acceptor in the biosynthetic pathway of sterols . Thus, cholesterol is absent from anaerobic bacteria (procaryotes). 

Huff, M.W., Pollex, R.L., Hegele, R.A. 2006. NPCILI evolution from pharmacological target to physiological sterol transporter. Arterioscler. Thromb. Vase. Biol. 26 2433-2438. 

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