Testing the paradigm that the denaturing effect of urea on protein stability is offset by methylamines at the physiological concentration ratio of 2:1 (urea:methylamines)

A current perspective on the compensatory effects of urea and methylamine on protein stability and function

“…However, this is not the real scenario because there are various evidences (as discussed below) wherein many proteins and enzymes fail to exhibit counteraction, and even the counteraction mechanism has been reported to be protein specific (Singh et al, 2007). It, therefore, appears that mechanism of counteraction is not a simple phenomenon as explained above.…”

“…Most of the studies carried out earlier have used T m (melting temperature) as a measure of protein stability and provided data on little or partial counteraction of proteins and enzymes by the 2:1 ratio of urea : methylamine. There is always a lag of 1-3 °C in T m in the presence of 2 M urea and 1 M TMAO (Burg, 2002;Lin and Timasheff, 1994;Singh et al, 2007;Yancey and Somero, 1979), which puts a question on the 2:1 ratio to be physiological one. However, based on T m measurements alone, this conclusion may not be valid as it is ∆G D 0 (value of ∆G D at physiological pH and 25 °C) , rather than T m , which is a proper index for measuring the perturbation of the denaturation equilibrium of proteins.…”

“…However, based on T m measurements alone, this conclusion may not be valid as it is ∆G D 0 (value of ∆G D at physiological pH and 25 °C) , rather than T m , which is a proper index for measuring the perturbation of the denaturation equilibrium of proteins. In this context, Ahmad and his coworkers (Singh et al, 2007) carried out the measurement of ∆G D 0 of three different proteins in the presence of urea and methylamines, (TMAO and sarcosine), singly and in combination at 2:1 molar ratio of urea:methylamine. Similar to earlier studies, partial counteraction was M A N U S C R I P T…”

“…Pertinently, it has been found that elasmobranches even during the embryo development accumulate both urea and TMAO together (Barton et al, 1999). Furthermore the mechanism of urea-methylamine counteraction has been understood in terms of thermodynamic, atomic and molecular levels (Burg and Peters, 1997;Burg et al, 1999;Kumar and Kishore, 2013;Lin and Timasheff, 1994;Meersman et al, 2009;Singh et al, 2007). In recent years, there has been no such article that addresses and discusses major developments on this front.…”

“…However, osmolytes other than methylamines must be tallied with these methylamines to achieve this ratio (Treberg et al, 2006). The urea-methylamine counteraction systems so far has been examined and found successfully working on (i) the thermal stability and functional activity of proteins/enzymes (Khan et al, 2013;Singh et al, 2007); (ii) thermal stability of Nucleic acids (tRNA) (Gluick and Yadav, 2003); (iii) the rate and extent of renaturation of acid denatured enzyme (Yancey and Somero, 1979); (iv) the reactivity of thiol groups of an enzyme (bovine glutamate dehydrogenase) (Yancey and Somero, 1979); (v) protein polymerisation (Tubulin and actin) (Hatori et al, 2014;Sackett, 1997;Tseng and Graves, 1998) and (vi) membrane fluidity (Barton et al, 1999), enzyme functional dynamics (Lactate dehydrogenase) (Zhadin and Callender, 2011) and aggregation of methane in aqueous solution (Sarma and Paul, 2012). Pertinently, it has been found that elasmobranches even during the embryo development accumulate both urea and TMAO together (Barton et al, 1999).…”