Activity and anion inhibition studies of the α-carbonic anhydrase from Thiomicrospira crunogena XCL-2 Gammaproteobacterium. Issue 21 (1st November 2015)

• Record Type: Journal Article
• Authors: Mahon, Brian P.; Díaz-Torres, Natalia A.; Pinard, Melissa A.; Tu, Chingkuang; Silverman, David N.; Scott, Kathleen M.; McKenna, Robert
• Is Part Of: Bioorganic & medicinal chemistry letters. Volume 25:Issue 21(2015)
• Page Start: 4937
• Page End: 4940
• Publication Date: 2015-11-01
• Subjects: Thiomicrospira crunogena XCL-2 -- α-Carbonic anhydrase -- Anions -- Mesophile -- CO2 hydration; Bioorganic chemistry -- Periodicals; Pharmaceutical chemistry -- Periodicals; 572
• DOI: 10.1016/j.bmcl.2015.05.001
• Languages: English
• ISSNs: 0960-894X

Abstract

Graphical abstract: The α-carbonic anhydrase (α-CA) from Thiomicrospira crunogena XCL-2 Gammaproteobacterium is an active CA that is readily inhibited by anions. Anionic inhibition of TcCA suggests a means for Thiomicrospira crunogena to shift its general metabolism. 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 K i values in the millimolar range (53–361 mM). Hydrogen sulfide (HS − ) revealed the highest affinity for TcruCA with a K i 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 .