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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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Structure of the active site. Superimposition of the active site residues in psychrophilic (blue) and mesophilic α-amylases (red). The chloride and calcium ions are shown as blue and green spheres, respectively. The 24 residues performing direct or water-mediated interactions with the substrate analog derived from acarbose (yellow) are identical and superimpose perfectly within the resolution of the structures, demonstrating a structural identity in these psychrophilic and mesophilic enzymes [27].
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f3-ijms-13-11643: Structure of the active site. Superimposition of the active site residues in psychrophilic (blue) and mesophilic α-amylases (red). The chloride and calcium ions are shown as blue and green spheres, respectively. The 24 residues performing direct or water-mediated interactions with the substrate analog derived from acarbose (yellow) are identical and superimpose perfectly within the resolution of the structures, demonstrating a structural identity in these psychrophilic and mesophilic enzymes [27].

Mentions: Crystal structures of psychrophilic enzymes were of course of prime importance to investigate the properties of these heat-labile and cold-active catalytic centers. The first basic observation is that all side chains involved in the catalytic mechanism are strictly conserved. Indeed, comparison of the first X-ray structure of a psychrophilic enzyme, the cold-active -amylase [23,24], and of its closest structural homologue from pig both in complex with acarbose, a pseudosaccharide inhibitor mimicking the transition state intermediate [25,26], has shown that all 24 residues forming the catalytic cleft are strictly conserved in the cold-active α-amylase (Figure 3). This outstanding example of active site identity demonstrates that the specific properties of psychrophilic enzymes can be reached without any amino acid substitution in the reaction center. As a consequence, changes occurring elsewhere in the molecule are responsible for the optimization of the catalytic parameters (see Section 4).


Optimization to low temperature activity in psychrophilic enzymes.

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

Structure of the active site. Superimposition of the active site residues in psychrophilic (blue) and mesophilic α-amylases (red). The chloride and calcium ions are shown as blue and green spheres, respectively. The 24 residues performing direct or water-mediated interactions with the substrate analog derived from acarbose (yellow) are identical and superimpose perfectly within the resolution of the structures, demonstrating a structural identity in these psychrophilic and mesophilic enzymes [27].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3-ijms-13-11643: Structure of the active site. Superimposition of the active site residues in psychrophilic (blue) and mesophilic α-amylases (red). The chloride and calcium ions are shown as blue and green spheres, respectively. The 24 residues performing direct or water-mediated interactions with the substrate analog derived from acarbose (yellow) are identical and superimpose perfectly within the resolution of the structures, demonstrating a structural identity in these psychrophilic and mesophilic enzymes [27].
Mentions: Crystal structures of psychrophilic enzymes were of course of prime importance to investigate the properties of these heat-labile and cold-active catalytic centers. The first basic observation is that all side chains involved in the catalytic mechanism are strictly conserved. Indeed, comparison of the first X-ray structure of a psychrophilic enzyme, the cold-active -amylase [23,24], and of its closest structural homologue from pig both in complex with acarbose, a pseudosaccharide inhibitor mimicking the transition state intermediate [25,26], has shown that all 24 residues forming the catalytic cleft are strictly conserved in the cold-active α-amylase (Figure 3). This outstanding example of active site identity demonstrates that the specific properties of psychrophilic enzymes can be reached without any amino acid substitution in the reaction center. As a consequence, changes occurring elsewhere in the molecule are responsible for the optimization of the catalytic parameters (see Section 4).

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