osmolyte

{{Short description|Organic compounds that influence the properties of biological fluids}}

Osmolytes are low-molecular-weight organic compounds that influence the properties of biological fluids. Osmolytes are a class of organic molecules that play a significant role in regulating osmotic pressure and maintaining cellular homeostasis in various organisms, particularly in response to environmental stressors.{{cite journal|title=Organic osmolytes as compatible, metabolic and counteracting cytoprotectants in high osmolarity and other stresses|author=Paul H. Yancey|journal=Journal of Experimental Biology|year=2005|volume=208|issue=15|pages= 2819–2830|

doi=10.1242/jeb.01730|pmid=16043587|doi-access=free|bibcode=2005JExpB.208.2819Y }} Their primary role is to maintain the integrity of cells by affecting the viscosity, melting point, and ionic strength of the aqueous solution. When a cell swells due to external osmotic pressure, membrane channels open and allow efflux of osmolytes carrying water, restoring normal cell volume.

These molecules are involved in counteracting the effects of osmotic stress, which occurs when there are fluctuations in the concentration of solutes (such as ions and sugars) inside and outside cells. Osmolytes help cells adapt to changing osmotic conditions, thereby ensuring their survival and functionality.Review of Medical Physiology, William F. Ganong, McGraw-Hill Medical, {{ISBN|978-0-07-144040-0}}. Osmolytes also interact with the constituents of the cell, e.g., they influence protein folding.{{cite journal | vauthors=Bolen DW, Baskakov IV | title=The osmophobic effect: natural selection of a thermodynamic force in protein folding | journal=Journal of Molecular Biology | volume=310 | issue=5 | year=2001 | pages=955–963 | doi=10.1006/jmbi.2001.4819 | pmid=11502004}}{{Cite book|last=Su |first= Zhaoqian |url=https://digitalcommons.njit.edu/dissertations/48/|title=Roles of cosolvents on protein stability|work= Dissertations |year=2017|oclc=1245504372}} Common osmolytes include amino acids, sugars and polyols, methylamines, methylsulfonium compounds, and urea.

Case studies

Natural osmolytes that can act as osmoprotectants include trimethylamine N-oxide (TMAO), dimethylsulfoniopropionate, sarcosine, betaine, glycerophosphorylcholine, myo-inositol, taurine, glycine, and others.{{Cite journal

| last1 = Neuhofer | first1 = W.

| last2 = Beck | first2 = F. X.

| title = Survival in Hostile Environments: Strategies of Renal Medullary Cells

| doi = 10.1152/physiol.00003.2006

| journal = Physiology

| volume = 21

| issue = 3

| pages = 171–180

| year = 2006

| pmid = 16714475

}}{{cite journal |vauthors=Arakawa T, Timasheff SN | title=The stabilization of proteins by osmolytes | journal=Biophysical Journal | volume=47 | issue=3 | year=1985 | pages=411–414 | pmc = 1435219 | doi=10.1016/s0006-3495(85)83932-1 | pmid=3978211| bibcode=1985BpJ....47..411A}} Bacteria accumulate osmolytes for protection against a high osmotic environment.{{cite journal | author=Csonka LN | title=Physiological and genetic responses of bacteria to osmotic stress | journal=Microbiology and Molecular Biology Reviews | volume=53 | issue=1 | year=1989 | pages=121–147| doi=10.1128/mr.53.1.121-147.1989 | pmc = 372720 | pmid=2651863}} The osmolytes are neutral non-electrolytes, except in bacteria that can tolerate salts. In humans, osmolytes are of particular importance in the renal medulla.{{Cite journal

| last1 = Gallazzini | first1 = M.

| last2 = Burg | first2 = M. B.

| doi = 10.1152/physiol.00009.2009

| title = What's New About Osmotic Regulation of Glycerophosphocholine

| journal = Physiology

| volume = 24

| issue = 4

| pages = 245–249

| year = 2009

| pmid = 19675355

| pmc =2943332

}}

Osmolytes are present in the cells of fish, and function to protect the cells from water pressure. As the osmolyte concentration in fish cells scales linearly with pressure and therefore depth, osmolytes have been used to calculate the maximum depth where a fish can survive. Fish cells reach a maximum concentration of osmolytes at depths of approximately {{convert|26,900|ft|m|abbr=off|sp=us}}, with no fish ever being observed beyond {{convert|27,349|ft|m|abbr=off|sp=us}}.{{cite journal| title=Marine fish may be biochemically constrained from inhabiting the deepest ocean depths | journal=PNAS | year=2014 | volume=111 | issue=12 | pages=4461–4465 | doi=10.1073/pnas.1322003111 | pmid=24591588| vauthors=Yancey PH, Gerringer ME, Drazen JC, Rowden AA, Jamieson A| bibcode=2014PNAS..111.4461Y | pmc=3970477 | doi-access=free}}{{cite news |last=Lu |first=Donna |date=3 April 2023 |title=Scientists find deepest fish ever recorded at 8,300 metres underwater near Japan |url=https://www.theguardian.com/environment/2023/apr/03/scientists-find-deepest-fish-ever-recorded-at-8300-metres-underwater-near-japan |work=The Guardian |location=London |access-date=25 May 2023}}

osmolyte

Case studies

References

Further reading