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Article: A rigidifying salt-bridge favors the activity of thermophilic enzyme at high temperatures at the expense of low-temperature activity

TitleA rigidifying salt-bridge favors the activity of thermophilic enzyme at high temperatures at the expense of low-temperature activity
Authors
Issue Date2011
PublisherPublic Library of Science. The Journal's web site is located at http://www.plosbiology.org/plosonline/?request=index-html
Citation
PLoS Biology, 2011, v. 9 n. 3, article no. e1001027 How to Cite?
AbstractBackground: Thermophilic enzymes are often less active than their mesophilic homologues at low temperatures. One hypothesis to explain this observation is that the extra stabilizing interactions increase the rigidity of thermophilic enzymes and hence reduce their activity. Here we employed a thermophilic acylphosphatase from Pyrococcus horikoshii and its homologous mesophilic acylphosphatase from human as a model to study how local rigidity of an active-site residue affects the enzymatic activity. Methods and Findings: Acylphosphatases have a unique structural feature that its conserved active-site arginine residue forms a salt-bridge with the C-terminal carboxyl group only in thermophilic acylphosphatases, but not in mesophilic acylphosphatases. We perturbed the local rigidity of this active-site residue by removing the salt-bridge in the thermophilic acylphosphatase and by introducing the salt-bridge in the mesophilic homologue. The mutagenesis design was confirmed by x-ray crystallography. Removing the salt-bridge in the thermophilic enzyme lowered the activation energy that decreased the activation enthalpy and entropy. Conversely, the introduction of the salt-bridge to the mesophilic homologue increased the activation energy and resulted in increases in both activation enthalpy and entropy. Revealed by molecular dynamics simulations, the unrestrained arginine residue can populate more rotamer conformations, and the loss of this conformational freedom upon the formation of transition state justified the observed reduction in activation entropy. Conclusions: Our results support the conclusion that restricting the active-site flexibility entropically favors the enzymatic activity at high temperatures. However, the accompanying enthalpy-entropy compensation leads to a stronger temperature-dependency of the enzymatic activity, which explains the less active nature of the thermophilic enzymes at low temperatures. © 2011 Lam et al.
Persistent Identifierhttp://hdl.handle.net/10722/157629
ISSN
2010 Impact Factor: 12.472
2015 SCImago Journal Rankings: 5.293
ISI Accession Number ID
Funding AgencyGrant Number
Research Grants Council, Hong Kong495005
476307
UGC
Hong KongSEG/CUHK08
Chinese University of Hong Kong
Funding Information:

This work was supported by grants from Research Grants Council, Hong Kong (Project no.: 495005, 476307), UGC Special Equipment Grants, Hong Kong (Project no.: SEG/CUHK08), and a strategic investment grant from the Chinese University of Hong Kong. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

References

 

DC FieldValueLanguage
dc.contributor.authorLam, SYen_US
dc.contributor.authorYeung, RCYen_US
dc.contributor.authorYu, THen_US
dc.contributor.authorSze, KHen_US
dc.contributor.authorWong, KBen_US
dc.date.accessioned2012-08-08T08:51:48Z-
dc.date.available2012-08-08T08:51:48Z-
dc.date.issued2011en_US
dc.identifier.citationPLoS Biology, 2011, v. 9 n. 3, article no. e1001027en_US
dc.identifier.issn1544-9173en_US
dc.identifier.urihttp://hdl.handle.net/10722/157629-
dc.description.abstractBackground: Thermophilic enzymes are often less active than their mesophilic homologues at low temperatures. One hypothesis to explain this observation is that the extra stabilizing interactions increase the rigidity of thermophilic enzymes and hence reduce their activity. Here we employed a thermophilic acylphosphatase from Pyrococcus horikoshii and its homologous mesophilic acylphosphatase from human as a model to study how local rigidity of an active-site residue affects the enzymatic activity. Methods and Findings: Acylphosphatases have a unique structural feature that its conserved active-site arginine residue forms a salt-bridge with the C-terminal carboxyl group only in thermophilic acylphosphatases, but not in mesophilic acylphosphatases. We perturbed the local rigidity of this active-site residue by removing the salt-bridge in the thermophilic acylphosphatase and by introducing the salt-bridge in the mesophilic homologue. The mutagenesis design was confirmed by x-ray crystallography. Removing the salt-bridge in the thermophilic enzyme lowered the activation energy that decreased the activation enthalpy and entropy. Conversely, the introduction of the salt-bridge to the mesophilic homologue increased the activation energy and resulted in increases in both activation enthalpy and entropy. Revealed by molecular dynamics simulations, the unrestrained arginine residue can populate more rotamer conformations, and the loss of this conformational freedom upon the formation of transition state justified the observed reduction in activation entropy. Conclusions: Our results support the conclusion that restricting the active-site flexibility entropically favors the enzymatic activity at high temperatures. However, the accompanying enthalpy-entropy compensation leads to a stronger temperature-dependency of the enzymatic activity, which explains the less active nature of the thermophilic enzymes at low temperatures. © 2011 Lam et al.en_US
dc.languageengen_US
dc.publisherPublic Library of Science. The Journal's web site is located at http://www.plosbiology.org/plosonline/?request=index-htmlen_US
dc.relation.ispartofPLoS Biologyen_US
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.titleA rigidifying salt-bridge favors the activity of thermophilic enzyme at high temperatures at the expense of low-temperature activityen_US
dc.typeArticleen_US
dc.identifier.emailSze, KH:khsze@hku.hken_US
dc.identifier.authoritySze, KH=rp00785en_US
dc.description.naturepublished_or_final_versionen_US
dc.identifier.doi10.1371/journal.pbio.1001027en_US
dc.identifier.scopuseid_2-s2.0-79953708228en_US
dc.identifier.hkuros211857-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-79953708228&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume9en_US
dc.identifier.issue3en_US
dc.identifier.isiWOS:000288942200014-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridLam, SY=8314272900en_US
dc.identifier.scopusauthoridYeung, RCY=13611815800en_US
dc.identifier.scopusauthoridYu, TH=37113513600en_US
dc.identifier.scopusauthoridSze, KH=7006735061en_US
dc.identifier.scopusauthoridWong, KB=7404759301en_US

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