title: Activity and anion inhibition studies of the α-carbonic anhydrase from Thiomicrospira crunogena XCL-2 Gammaproteobacterium.
abstract: Thiomicrospira crunogena XCL-2 expresses an α-carbonic anhydrase (TcruCA). Sequence alignments reveal that TcruCA displays a high sequence identity (>30%) relative to other α-CAs. This includes three conserved histidines that coordinate the active site zinc, a histidine proton shuttling residue, and opposing hydrophilic and hydrophobic sides that line the active site. The catalytic efficiency of TcruCA is considered moderate relative to other α-CAs (k(cat)/K(M)=1.1×10(7) M(-1) s(-1)), being a factor of ten less efficient than the most active α-CAs. TcruCA is also inhibited by anions with Cl(-), Br(-), and I(-), all showing Ki values in the millimolar range (53-361 mM). Hydrogen sulfide (HS(-)) revealed the highest affinity for TcruCA with a Ki of 1.1 μM. It is predicted that inhibition of TcruCA by HS(-) (an anion commonly found in the environment where Thiomicrospira crunogena is located) is a way for Thiomicrospira crunogena to regulate its carbon-concentrating mechanism (CCM) and thus the organism's metabolic functions. Results from this study provide preliminary insights into the role of TcruCA in the general metabolism of Thiomicrospira crunogena.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, 100 Newell Dr LG-171, Gainesville, FL 32610, United States.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Mahon
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, 100 Newell Dr LG-171, Gainesville, FL 32610, United States.
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, 100 Newell Dr LG-171, Gainesville, FL 32610, United States.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Pinard
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, 100 Newell Dr LG-171, Gainesville, FL 32610, United States.
authors.forename: Chingkuang
authors.initials: C
authors.lastname: Tu
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, United States.
authors.forename: David N
authors.initials: DN
authors.lastname: Silverman
authors.affiliation: Department of Integrated Biology, University of South Florida, Tampa, FL 33620, United States.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Scott
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, 100 Newell Dr LG-171, Gainesville, FL 32610, United States. Electronic address: rmckenna@ufl.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: McKenna
mesh_terms: D002257:Carbonic Anhydrase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002256:Carbonic Anhydrases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020563:Gammaproteobacteria / Q000201:enzymology*; D015394:Molecular Structure; D013329:Structure-Activity Relationship
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D002256:Carbonic Anhydrases
keywords: Anions; CO(2) hydration; Mesophile; Thiomicrospira crunogena XCL-2; α-Carbonic anhydrase