osmolytes

Osmolytes are small organic molecules that organisms accumulate in response to changes in environmental osmolarity to balance intracellular water with the surrounding medium. They are often referred to as compatible solutes because they can be accumulated to high levels without disrupting cellular metabolism or enzyme activity.

These compounds are synthesized or taken up from the environment and are found in bacteria, archaea, fungi, plants, algae, and some animals. Common osmolytes include proline, glycine betaine, trehalose, sucrose, sorbitol, mannitol, ectoine, and dimethylsulfoniopropionate (DMSP).

Functions include osmotic adjustment to prevent cell dehydration, stabilization of proteins and membranes under salt, heat, cold, or dehydration stress, and, in some cases, scavenging reactive oxygen species. They are categorized as compatible solutes because they typically do not interfere with metabolism even at high intracellular concentrations.

Biological and practical significance: in plants, osmolyte pathways contribute to drought and salt tolerance and are targets for breeding and genetic engineering. In biotechnology and medicine, osmolytes are used to stabilize proteins and enzymes, aid cryopreservation, and improve shelf life of formulations.

Research continues on the regulation of osmolyte biosynthesis and transport, their roles in stress signaling, and their impact on organismal fitness across environments.