Intracellular Organic Osmolytes: Function and Regulation

Abstract

Cells of almost all organisms accumulate organic osmolytes when exposed to hyperosmolality, most often in the form of high salt or urea. In this review, we discuss 1) how the organic osmolytes protect; 2) the identity of osmolytes in Archaea, bacteria, yeast, plants, marine animals, and mammals; 3) the mechanisms by which they are accumulated; 4) sensors of osmolality; 5) the signaling pathways involved; and 6) mutual counteraction by urea and methylamines.The function and regulation of intracellular organic osmolytes were already well described in a classical review 25 years ago (1). The basic concepts, as described then and still valid, are as follows. 1) All water-stressed organisms, except halobacteria, accumulate intracellular organic osmolytes in response to water stress. 2) The major systems of organic osmolytes include polyhydric alcohols, free amino acids and their derivatives, and combinations of urea and methylamines.3) The evolutionary advantage of the organic osmolyte systems is compatibility with macromolecular structure and function at high and variable osmolyte concentrations without modifying cellular proteins to function in concentrated intracellular solutions. 4) Osmolyte compatibility results from non-perturbing or favorable effects of osmolytes on macromolecule-solvent interactions. In this review, we emphasize subsequent findings that expand upon these concepts in various species.

Quantification of glycine betaine, choline and trimethylamine N-oxide in seawater particulates: Minimisation of seawater associated ion suppression

“…Betaine hydrochloride and choline dihydrogen citrate were purchased from Sigma Aldrich. Trimethylamine N-Oxide.2H 2 …”

“…Glycine betaine (GBT), trimethylamine N-oxide (TMAO) and choline are nitrogen-containing osmolytes (N-osmolytes) that are widely used by organisms in the marine environment to maintain favourable osmotic tension and positive turgor [1,2]. However, other roles for N-osmolytes are beginning to be elucidated.…”

Osmolyte modulated enhanced rice leaf catalase activity under salt-stress

“…Metabolically engineered transgenics, leading for increase synthesis and accumulation of osmolytes of various natures have been shown to protect the plant against salinity stress [22][23][24]. It is presumed that while maintaining the cell turgor pressure in salt-stressed plants, the osmolytes also behave as osmo-protectants towards membrane-protein complexes and enzyme-proteins, and protect them from salt-induced impairments [25].…”

Different strategies of osmoadaptation in the closely related marine myxobacteria Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1

“…proline and glutamate, and some specialized compatible solutes, e.g. betaine and ectoine (da Costa et al, 1998;Burg & Ferraris, 2008). Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) was discovered first in Ectothiorhodospira halochloris (Galinski, et al 1985) and later on in many bacterial species (Severin et al, 1992;Roberts, 2005).…”