Osmolytes classes

Table 6.1. Major Classes of Osmolytes and Their Distribution among Eukaryotes, Bacteria and Archaea. Elevated Concentrations of Osmolytes Due to Freeze-Avoidance ("Freezing") or Desiccation Stress (Artemia Embryos) Are Included...

The chemical properties that appear to underlie the fitness of the four classes of organic osmolytes include the following. First, these osmolytes are polar molecules that have high solubilities in water. They can be accumulated to high concentrations without unduly taxing the solvent capacity of the cell. Glycerol,... 

Figure 6.2. (Upper panel) The four major classes of organic osmolytes (I) sugars and polyhydric alcohols (polyols) (II) amino acids and amino acid derivatives (III) methylated ammonium and sulfonium compounds and (IV) urea. (Figure modified after Somero and Yancey, 1997.) (Lower panel) Structures of charged osmolytes accumulated in extremely halophilic archaea (after Martin et al., 1999). Note that these osmolytes commonly represent a type of organic osmolyte that is found in many bacteria or eukaryotes to which a charged group has been attached. Typically, the charged group is anionic, for example, a phosphate or a carboxylate group.

Sucrose is a compatible osmolyte, belonging to a class of low molecular weight compounds (C12H22O11) present both in prokaryotic and eukaryotic cells in order to protect proteins against aggressive effects of harsh environmental conditions such as cold and heat stress [1,2],... 

Synthesis of compatible solutes and production of stress-tolerant plants The cellular response of salt- and drought-tolerant organisms to both long- and short-term sah-nity stresses includes the synthesis and accumulation of a class of osmoprotective compounds known as compatible solutes. These relatively small, organic osmolytes include amino acids and derivatives, polyols and sugars, and methylamines. The osmolytes stabilize proteins and cellular stractures, and can also increase the osmotic pressure of the ceU [45]. This response... 

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