Portal de Periódicos da CAPES

Biochemistry and Physiology of Hopanoids in Bacteria

1993; Elsevier BV; Linguagem: Inglês

10.1016/s0065-2911(08)60100-9

2162-5468

Hermann Sahm, Michel Rohmer, Stephanie Bringer‐Meyer, Georg A. Sprenger, Roland Welle,

Porphyrin Metabolism and Disorders

Hopanoids are amphipathic components of bacterial cell membranes and maintain membrane stability by increasing rigidity in the lipid matrix. Thus, the function of hopanoids in bacteria is analogous to that of membrane sterols in eukaryotes. Biosynthesis of hopanoids does not require oxygen during squalene cyclization and other reactions. This chapter describes the structures, distribution, and physiological role of hopanoids as membrane stabilizers. Structural variations in hopanoids result from linkage between a hydrophobic triterpenic moiety and a polar side-chain. The simplest hopanoids, diplopterol and diploptene, are readily extractable from freeze-dried cells by organic solvents and can be characterized by gas-liquid chromatography (GLC) and by combined GLC-mass spectroscopy. Another methods for analysis of periodate-oxidized and borohydride-reduced hopanoids, where hopanoid alcohols are converted into benzoate or naphthoate derivatives, yielding chromogenic compounds that can be separated with a reversed-phase high-pressure liquid chromatography (HPLC) system using ultraviolet-radiation detection are presented. Hopanoid-containing fractions can usually be detected only by proton nuclear magnetic-resonance (NMR) spectroscopy exploiting the characteristic pattern of methyl singlets in the hopane skeleton. The occurrence of hopanoids in the specialized organisms exemplifies their general role as membrane reinforcers in eubacteria. The presence of hopanoids is essential for survival of the bacteria that contain them. The chapter accounts for the biosynthesis and principles of genetics for the hopanoids. Hopanoids are abundant natural products of eubacteria. The lipid family of hopanoids consists of numerous structural variants that lead to their detection and analysis.