title: Structural and biophysical characterization of the α-carbonic anhydrase from the gammaproteobacterium Thiomicrospira crunogena XCL-2: insights into engineering thermostable enzymes for CO2 sequestration.
abstract: Biocatalytic CO2 sequestration to reduce greenhouse-gas emissions from industrial processes is an active area of research. Carbonic anhydrases (CAs) are attractive enzymes for this process. However, the most active CAs display limited thermal and pH stability, making them less than ideal. As a result, there is an ongoing effort to engineer and/or find a thermostable CA to fulfill these needs. Here, the kinetic and thermal characterization is presented of an α-CA recently discovered in the mesophilic hydrothermal vent-isolate extremophile Thiomicrospira crunogena XCL-2 (TcruCA), which has a significantly higher thermostability compared with human CA II (melting temperature of 71.9°C versus 59.5°C, respectively) but with a tenfold decrease in the catalytic efficiency. The X-ray crystallographic structure of the dimeric TcruCA shows that it has a highly conserved yet compact structure compared with other α-CAs. In addition, TcruCA contains an intramolecular disulfide bond that stabilizes the enzyme. These features are thought to contribute significantly to the thermostability and pH stability of the enzyme and may be exploited to engineer α-CAs for applications in industrial CO2 sequestration.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Díaz-Torres
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Mahon
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Boone
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Pinard
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Chingkuang
authors.initials: C
authors.lastname: Tu
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Ng
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Mavis
authors.initials: M
authors.lastname: Agbandje-McKenna
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: David
authors.initials: D
authors.lastname: Silverman
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Scott
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: McKenna
mesh_terms: D055162:Biocatalysis; D002245:Carbon Dioxide / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D020563:Gammaproteobacteria / Q000737:chemistry* / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D015202:Protein Engineering; D055503:Protein Multimerization; D013696:Temperature
chemical_list: D002245:Carbon Dioxide; D002256:Carbonic Anhydrases
keywords: CO2 sequestration; Thiomicrospira crunogena XCL-2; biocatalyst; extremophile; protein thermostability; α-carbonic anhydrase