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https://www.ias.ac.in/article/fulltext/jbsc/034/02/0321-0331

Enzyme activity; methylamine osmolytes; preferential hydration; protein denaturation; protein stability; urea

Intracellular organic osmolytes are present in certain organisms adapted to harsh environments. These osmolytes protect intracellular macromolecules against denaturing environmental stress. In contrast to the usually benign effects of most organic osmolytes, the waste product urea is a well-known perturbant of macromolecules. Although urea is a perturbing solute which inhibits enzyme activity and stability, it is employed by some species as a major osmolyte. The answer to this paradox was believed to be the discovery of protective osmolytes (methylamines). We review the current state of knowledge on the various ways of counteracting the harmful effects of urea in nature and the mechanisms for this. This review ends with the mechanistic idea that cellular salt (KCl/NaCl) plays a crucial role in counteracting the effects of urea, either by inducing required chaperones or methylamines, or by thermodynamic interactions with urea-destabilised proteins. We also propose future opportunities and challenges in the field.

Laishram R Singh¹ Tanveer Ali Dar² Faizan Ahmad²

1. Division of Population Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
2. Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi 110 025, India

Published

June 2009

Manuscript received

12 November 2008

Accepted

13 February 2009

Early published

21 March 2009