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Optimization to low temperature activity in psychrophilic enzymes.

Struvay C, Feller G - Int J Mol Sci (2012)

Bottom Line: Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state.In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule.This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry, Centre for Protein Engineering, University of Liège, Institute of Chemistry B6a, B-4000 Liège-Sart Tilman, Belgium; E-Mail: cstruvay@ulg.ac.be.

ABSTRACT
Psychrophiles, i.e., organisms thriving permanently at near-zero temperatures, synthesize cold-active enzymes to sustain their cell cycle. These enzymes are already used in many biotechnological applications requiring high activity at mild temperatures or fast heat-inactivation rate. Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state. Furthermore, a weak temperature dependence of activity ensures moderate reduction of the catalytic activity in the cold. In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule. This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold. Considering the subtle structural adjustments required for low temperature activity, directed evolution appears to be the most suitable methodology to engineer cold activity in biological catalysts.

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Related in: MedlinePlus

Optimization of activity by decreasing substrate affinity in psychrophilic enzymes. Reaction profile for an enzyme-catalyzed reaction with Gibbs energy changes under saturating substrate concentration. Weak substrate binding (in blue) decreases the activation energy (ΔG#psychro) and thereby increases the reaction rate. In this scheme, the energy levels of E + S and of ES# are assumed to be similar [10].
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f4-ijms-13-11643: Optimization of activity by decreasing substrate affinity in psychrophilic enzymes. Reaction profile for an enzyme-catalyzed reaction with Gibbs energy changes under saturating substrate concentration. Weak substrate binding (in blue) decreases the activation energy (ΔG#psychro) and thereby increases the reaction rate. In this scheme, the energy levels of E + S and of ES# are assumed to be similar [10].

Mentions: Referring to Equation 1, the high activity of cold-adapted enzymes corresponds to a decrease of the free energy of activation ΔG#. Two strategies have been highlighted to reduce the height of this energy barrier. Figure 4 illustrates the first strategy where an evolutionary pressure increases Km in order to maximize the reaction rate. According to the transition state theory, when the enzyme encounters its substrate, the enzyme-substrate complex ES falls into an energy pit. For the reaction to proceed, an activated state ES# has to be reached, that eventually breaks down into the enzyme and the product. The height of the energy barrier between the ground state ES and the transition state ES# is defined as the free energy of activation ΔG#: the lower this barrier, the higher the activity as reflected in Equation 1. In the case of cold active enzymes displaying a weak affinity for the substrate, the energy pit for the ES complex is less deep (dashed in Figure 4). It follows that the magnitude of the energy barrier is reduced and therefore the activity is increased. This thermodynamic link between affinity and activity is valid for most enzymes (extremophilic or not) under saturating substrate concentrations and this link appears to be involved in the improvement of activity at low temperatures in numerous cold-active enzymes [17,59].


Optimization to low temperature activity in psychrophilic enzymes.

Struvay C, Feller G - Int J Mol Sci (2012)

Optimization of activity by decreasing substrate affinity in psychrophilic enzymes. Reaction profile for an enzyme-catalyzed reaction with Gibbs energy changes under saturating substrate concentration. Weak substrate binding (in blue) decreases the activation energy (ΔG#psychro) and thereby increases the reaction rate. In this scheme, the energy levels of E + S and of ES# are assumed to be similar [10].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472767&req=5

f4-ijms-13-11643: Optimization of activity by decreasing substrate affinity in psychrophilic enzymes. Reaction profile for an enzyme-catalyzed reaction with Gibbs energy changes under saturating substrate concentration. Weak substrate binding (in blue) decreases the activation energy (ΔG#psychro) and thereby increases the reaction rate. In this scheme, the energy levels of E + S and of ES# are assumed to be similar [10].
Mentions: Referring to Equation 1, the high activity of cold-adapted enzymes corresponds to a decrease of the free energy of activation ΔG#. Two strategies have been highlighted to reduce the height of this energy barrier. Figure 4 illustrates the first strategy where an evolutionary pressure increases Km in order to maximize the reaction rate. According to the transition state theory, when the enzyme encounters its substrate, the enzyme-substrate complex ES falls into an energy pit. For the reaction to proceed, an activated state ES# has to be reached, that eventually breaks down into the enzyme and the product. The height of the energy barrier between the ground state ES and the transition state ES# is defined as the free energy of activation ΔG#: the lower this barrier, the higher the activity as reflected in Equation 1. In the case of cold active enzymes displaying a weak affinity for the substrate, the energy pit for the ES complex is less deep (dashed in Figure 4). It follows that the magnitude of the energy barrier is reduced and therefore the activity is increased. This thermodynamic link between affinity and activity is valid for most enzymes (extremophilic or not) under saturating substrate concentrations and this link appears to be involved in the improvement of activity at low temperatures in numerous cold-active enzymes [17,59].

Bottom Line: Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state.In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule.This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry, Centre for Protein Engineering, University of Liège, Institute of Chemistry B6a, B-4000 Liège-Sart Tilman, Belgium; E-Mail: cstruvay@ulg.ac.be.

ABSTRACT
Psychrophiles, i.e., organisms thriving permanently at near-zero temperatures, synthesize cold-active enzymes to sustain their cell cycle. These enzymes are already used in many biotechnological applications requiring high activity at mild temperatures or fast heat-inactivation rate. Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state. Furthermore, a weak temperature dependence of activity ensures moderate reduction of the catalytic activity in the cold. In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule. This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold. Considering the subtle structural adjustments required for low temperature activity, directed evolution appears to be the most suitable methodology to engineer cold activity in biological catalysts.

Show MeSH
Related in: MedlinePlus