The catalytic properties of human carbonic anhydrase IX.
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.
Wingo
T
T
Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida 32610-0267, USA.
Tu
C
C
Laipis
P J
PJ
Silverman
D N
DN
D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D002384:Catalysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005016:Ethoxzolamide / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020539:Sequence Analysis, Protein
D000951:Antigens, Neoplasm; D004791:Enzyme Inhibitors; D009363:Neoplasm Proteins; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D005016:Ethoxzolamide