The catalytic properties of human carbonic anhydrase IX

Biochem Biophys Res Commun. 2001 Nov 2;288(3):666-9. doi: 10.1006/bbrc.2001.5824.


Human carbonic anhydrase IX (CA IX) is an integral membrane protein and a member of the alpha class of carbonic anhydrases that includes the human and animal enzymes. We have prepared a truncated, recombinant form of human CA IX of 255 residues consistent with full-length human CA II, among the most efficient of the carbonic anhydrases. Catalysis by and inhibition of this form of human CA IX has been investigated using stopped-flow spectrophotometry and 18O exchange measured by mass spectrometry. In kinetic constants for the hydration of CO2, CA IX closely resembled CA II with maximal proton transfer-dependent 18O exchange near 1 micros(-1) and kcat/Km near 55 microM(-1) x s(-1). Human CA IX was very strongly inhibited by three classic sulfonamides and cyanate, with inhibition constants that are close to those for CA II.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Antigens, Neoplasm*
  • Carbonic Anhydrase IX
  • Carbonic Anhydrases*
  • Catalysis
  • Enzyme Inhibitors / pharmacology
  • Ethoxzolamide / pharmacology
  • Humans
  • Hydrogen-Ion Concentration
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / metabolism*
  • Sequence Analysis, Protein


  • Antigens, Neoplasm
  • Enzyme Inhibitors
  • Neoplasm Proteins
  • CA9 protein, human
  • Carbonic Anhydrase IX
  • Carbonic Anhydrases
  • Ethoxzolamide