Activity and anion inhibition studies of the α-carbonic anhydrase from Thiomicrospira crunogena XCL-2 Gammaproteobacterium

Bioorg Med Chem Lett. 2015 Nov 1;25(21):4937-4940. doi: 10.1016/j.bmcl.2015.05.001. Epub 2015 May 6.


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.

Keywords: Anions; CO(2) hydration; Mesophile; Thiomicrospira crunogena XCL-2; α-Carbonic anhydrase.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carbonic Anhydrase Inhibitors / chemical synthesis
  • Carbonic Anhydrase Inhibitors / chemistry
  • Carbonic Anhydrase Inhibitors / pharmacology*
  • Carbonic Anhydrases / metabolism*
  • Dose-Response Relationship, Drug
  • Gammaproteobacteria / enzymology*
  • Molecular Structure
  • Structure-Activity Relationship


  • Carbonic Anhydrase Inhibitors
  • Carbonic Anhydrases