Synchrotron Radiation Provides a Plausible Explanation for the Generation of a Free Radical Adduct of Thioxolone in Mutant Carbonic Anhydrase II.
Thioxolone acts as a prodrug in the presence of carbonic anhydrase II (CA II), whereby the molecule is cleaved by thioester hydrolysis to the carbonic anhydrase inhibitor, 4-mercaptobenzene-1,3-diol (TH0). Thioxolone was soaked into the proton transfer mutant H64A of CA II in an effort to capture a reaction intermediate via X-ray crystallography. Structure determination of the 1.2 Å resolution data revealed the TH0 had been modified to a 4,4'-disulfanediyldibenzene-1,3-diol, a product of crystallization conditions, and a zinc ligated 2,4-dihydroxybenzenesulfenic acid, most likely induced by radiation damage. Neither ligand was likely a result of an enzymatic mechanism.
Sippel
Katherine H
KH
Department of Biochemistry and Molecular Biology, P.O. Box 100245, College of Medicine, University of Florida, Gainesville, Florida 32610.
Genis
Caroli
C
Govindasamy
Lakshmanan
L
Agbandje-McKenna
Mavis
M
Kiddle
James J
JJ
Tripp
Brian C
BC
McKenna
Robert
R