Effect of osmoregulatory solutes on the stability of proteins

Gopal, Swarita; Ahluwalia, J. C.

doi:10.1039/ft9938902769

Cited by 23 publications

(22 citation statements)

References 23 publications

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“…There are two separable issues in the counteraction hypothesis, one dealing with the action of TMAO in stabilizing proteins against urea-induced denaturation, and the other dealing with the action of TMAO in counteracting effects of urea on the functional activity of proteins. A broad body of work on protein stabilization has established that TMAO indeed stabilizes proteins against urea-induced denaturation (Gopal and Ahluwalia, 1993;Lin and Timasheff, 1994;Wang and Bolen, 1997;Yancey and Somero, 1979). Our own work strongly indicates that the origin of the ability of TMAO to thermodynamically stabilize proteins against urea-induced denaturation is due to the highly unfavorable interaction of TMAO with the peptide backbone of the denatured state (Wang and Bolen, 1997).…”

Section: Discussionmentioning

confidence: 62%

Trimethylamine-N-Oxide Counteracts Urea Effects on Rabbit Muscle Lactate Dehydrogenase Function: A Test of the Counteraction Hypothesis

Baskakov

Wang

Bolen

1998

Biophysical Journal

138

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Trimethylamine-N-oxide (TMAO) in the cells of sharks and rays is believed to counteract the deleterious effects of the high intracellular concentrations of urea in these animals. It has been hypothesized that TMAO has the generic ability to counteract the effects of urea on protein structure and function, regardless of whether that protein actually evolved in the presence of these two solutes. Rabbit muscle lactate dehydrogenase (LDH) did not evolve in the presence of either solute, and it is used here to test the validity of the counteraction hypothesis. With pyruvate as substrate, results show that its Km and the combined Km of pyruvate and NADH are increased by urea, decreased by TMAO, and in 1:1 and 2:1 mixtures of urea:TMAO the Km values are essentially equivalent to the Km values obtained in the absence of the two solutes. In contrast, values of k(cat) and the Km for NADH as a substrate are unperturbed by urea, TMAO, or urea:TMAO mixtures. All of these effects are consistent with TMAO counteraction of the effects of urea on LDH kinetic parameters, supporting the premise that counteraction is a property of the solvent system and is independent of the evolutionary history of the protein.

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Section: Discussionmentioning

confidence: 62%

Trimethylamine-N-Oxide Counteracts Urea Effects on Rabbit Muscle Lactate Dehydrogenase Function: A Test of the Counteraction Hypothesis

Baskakov

Wang

Bolen

1998

Biophysical Journal

138

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“…The relative error in determination of all thermodynamic quantities at 25~ is estimated to be • It is well known that thermodynamic stability of small globular proteins decreases with increasing urea concentration (Makhatadze and Privalov, 1992;Gopal and Ahluwalia, 1991). Unfortunately, there are no literature data on the thermal stability of globular proteins in the presence of alkylureas except those of fl-lactoglobulin (Poklar et al, 1993).…”

Section: Effect Of Different Ureas On Thermal Stability Of O~-ctg a Omentioning

confidence: 99%

Thermodynamics of denaturation of α-chymotrypsinogen A in aqueous urea and alkylurea solutions

1995

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The effects of pH, urea, and alkylureas on the thermal stability of alpha-chymotrypsinogen A (alpha-ctg A) have been investigated by differential scanning calorimetry (DSC) and UV spectroscopy. Heat capacity changes and enthalpies of transition of alpha-ctg A in the presence of urea and alkylureas were measured at the transition temperature. Using these data, the corresponding Gibbs free energies, enthalpies, and entropies of denaturation at 25 degrees C were calculated. Comparison of these values shows that at 25 degrees C denaturation with urea is characterized by a significantly smaller enthalpy and entropy of denaturation. At all denaturant concentrations the enthalpy term slightly dominates the entropy term in the Gibbs free energy function. The most obvious effect of alkylureas was lowering of the temperature of transition, which was increasing with alkylurea concentration and the size of alkyl chain. Destabilization of the folded protein in the presence of alkylureas appears to be primarily the result of the weakening of hydrophobic interactions due to diminished solvent ordering around the protein-molecules. At pH lower than 2.0, alpha-ctg A still exists in a very stable form, probably the acid-denatured from (A-form).

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“…Many of the efforts to investigate the effects of osmolytes on protein function have focused on k cat , K m , and K i parameters of enzymes (Burg et al, 1996;de Meis, 1988;Gopal and Ahluwalia, 1993;Lin and Timasheff, 1994;Santoro et al, 1992;Wang and Bolen, 1996;Yancey andSomero, 1979, 1980). These parameters are assumed to be timeindependent, but the manner in which such data are collected can unwittingly incorporate time-dependent effects into the measurements.…”

Section: Introductionmentioning

confidence: 99%

Time-Dependent Effects of Trimethylamine-N-Oxide/Urea on Lactate Dehydrogenase Activity: An Unexplored Dimension of the Adaptation Paradigm

Baskakov

Bolen

1998

Biophysical Journal

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Given that enzymes in urea-rich cells are believed to be just as sensitive to urea effects as enzymes in non-urea-rich cells, it is argued that time-dependent inactivation of enzymes by urea could become a factor of overriding importance in the biology of urea-rich cells. Time-independent parameters (e.g. Tm, k(cat), and Km) involving protein stability and enzyme function have generally been the focus of inquiries into the efficacy of naturally occurring osmolytes like trimethylamine-N-oxide (TMAO), to offset the deleterious effects of urea on the intracellular proteins in the urea-rich cells of elasmobranchs. However, using urea concentrations found in urea-rich cells of elasmobranches, we have found time-dependent effects on lactate dehydrogenase activity which indicate that TMAO plays the important biological role of slowing urea-induced dissociation of multimeric intracellular proteins. TMAO greatly diminishes the rate of lactate dehydrogenase dissociation and affords significant protection of the enzyme against urea-induced time-dependent inactivation. The effects of TMAO on enzyme inactivation by urea adds a temporal dimension that is an important part of the biology of the adaptation paradigm.

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Effect of osmoregulatory solutes on the stability of proteins

Cited by 23 publications

References 23 publications

Trimethylamine-N-Oxide Counteracts Urea Effects on Rabbit Muscle Lactate Dehydrogenase Function: A Test of the Counteraction Hypothesis

Trimethylamine-N-Oxide Counteracts Urea Effects on Rabbit Muscle Lactate Dehydrogenase Function: A Test of the Counteraction Hypothesis

Thermodynamics of denaturation of α-chymotrypsinogen A in aqueous urea and alkylurea solutions

Time-Dependent Effects of Trimethylamine-N-Oxide/Urea on Lactate Dehydrogenase Activity: An Unexplored Dimension of the Adaptation Paradigm

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