2OSF

Inhibition of Carbonic Anhydrase II by Thioxolone: A Mechanistic and Structural Study


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.60 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.164 

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This is version 1.1 of the entry. See complete history


Literature

Inhibition of carbonic anhydrase II by thioxolone: a mechanistic and structural study.

Barrese, A.A.Genis, C.Fisher, S.Z.Orwenyo, J.N.Kumara, M.T.Dutta, S.K.Phillips, E.Kiddle, J.J.Tu, C.Silverman, D.N.Govindasamy, L.Agbandje-McKenna, M.McKenna, R.Tripp, B.C.

(2008) Biochemistry 47: 3174-3184

  • DOI: 10.1021/bi702385k
  • Primary Citation of Related Structures:  
    2OSF, 2OSM

  • PubMed Abstract: 
  • This paper examines the functional mechanism of thioxolone, a compound recently identified as a weak inhibitor of human carbonic anhydrase II by Iyer et al. (2006) J. Biomol. Screening 11, 782-791 . Thioxolone lacks sulfonamide, sulfamate, or hydroxamate functional groups that are typically found in therapeutic carbonic anhydrase (CA) inhibitors, such as acetazolamide ...

    This paper examines the functional mechanism of thioxolone, a compound recently identified as a weak inhibitor of human carbonic anhydrase II by Iyer et al. (2006) J. Biomol. Screening 11, 782-791 . Thioxolone lacks sulfonamide, sulfamate, or hydroxamate functional groups that are typically found in therapeutic carbonic anhydrase (CA) inhibitors, such as acetazolamide. Analytical chemistry and biochemical methods were used to investigate the fate of thioxolone upon binding to CA II, including Michaelis-Menten kinetics of 4-nitrophenyl acetate esterase cleavage, liquid chromatography-mass spectrometry (LC-MS), oxygen-18 isotope exchange studies, and X-ray crystallography. Thioxolone is proposed to be a prodrug inhibitor that is cleaved via a CA II zinc-hydroxide mechanism known to catalyze the hydrolysis of esters. When thioxolone binds in the active site of CA II, it is cleaved and forms 4-mercaptobenzene-1,3-diol via the intermediate S-(2,4-thiophenyl)hydrogen thiocarbonate. The esterase cleavage product binds to the zinc active site via the thiol group and is therefore the active CA inhibitor, while the intermediate is located at the rim of the active-site cavity. The time-dependence of this inhibition reaction was investigated in detail. Because this type of prodrug inhibitor mechanism depends on cleavage of ester bonds, this class of inhibitors may have advantages over sulfonamides in determining isozyme specificity. A preliminary structure-activity relationship study with a series of structural analogues of thioxolone yielded similar estimates of inhibition constants for most compounds, although two compounds with bromine groups at the C1 carbon of thioxolone were not inhibitory, suggesting a possible steric effect.


    Organizational Affiliation

    Department of Biological Sciences, Mailstop 5410, College of Arts and Sciences, 1903 West Michigan Avenue, Western Michigan University, Kalamazoo, Michigan 49008-5410, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Carbonic anhydrase 2A259Homo sapiensMutation(s): 0 
Gene Names: CA2
EC: 4.2.1.1
UniProt & NIH Common Fund Data Resources
Find proteins for P00918 (Homo sapiens)
Explore P00918 
Go to UniProtKB:  P00918
PHAROS:  P00918
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
S24 (Subject of Investigation/LOI)
Query on S24

Download Ideal Coordinates CCD File 
D [auth A]S-(2,4-dihydroxyphenyl) hydrogen thiocarbonate
C7 H6 O4 S
MFTAINZKTCOZPX-UHFFFAOYSA-N
 Ligand Interaction
TH0
Query on TH0

Download Ideal Coordinates CCD File 
C [auth A]4-MERCAPTOBENZENE-1,3-DIOL
C6 H6 O2 S
XFTQIEMOLHJTFV-UHFFFAOYSA-N
 Ligand Interaction
ZN
Query on ZN

Download Ideal Coordinates CCD File 
B [auth A]ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
Binding Affinity Annotations 
IDSourceBinding Affinity
TH0 PDBBind:  2OSF Ki: 1.48e+5 (nM) from 1 assay(s)
Binding MOAD:  2OSF Ki: 1.48e+5 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.60 Å
  • R-Value Free: 0.211 
  • R-Value Work: 0.164 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 42.751α = 90
b = 41.705β = 104.65
c = 72.877γ = 90
Software Package:
Software NamePurpose
CrystalCleardata collection
CNSrefinement
SHELXL-97refinement
DENZOdata reduction
SCALEPACKdata scaling
CNSphasing

Structure Validation

View Full Validation Report




Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-05-27
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance