Design of a carbonic anhydrase IX active-site mimic to screen inhibitors for possible anticancer properties.

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Genis C, Sippel KH, Case N, Cao W, Avvaru BS, Tartaglia LJ, Govindasamy L, Tu C, Agbandje-McKenna M, Silverman DN, Rosser CJ, McKenna R

Design of a carbonic anhydrase IX active-site mimic to screen inhibitors for possible anticancer properties.

Biochemistry. 2009 Feb 17;48(6):1322-31. doi: 10.1021/bi802035f.

PubMed ID

19170619 [ View in PubMed

]

Abstract

Recently, a convincing body of evidence has accumulated suggesting that the overexpression of carbonic anhydrase isozyme IX (CA IX) in some cancers contributes to the acidification of the extracellular matrix, which in turn promotes the growth and metastasis of the tumor. These observations have made CA IX an attractive drug target for the selective treatment of certain cancers. Currently, there is no available X-ray crystal structure of CA IX, and this lack of availability has hampered the rational design of selective CA IX inhibitors. In light of these observations and on the basis of structural alignment homology, using the crystal structure of carbonic anhydrase II (CA II) and the sequence of CA IX, a double mutant of CA II with Ala65 replaced by Ser and Asn67 replaced by Gln has been constructed to resemble the active site of CA IX. This CA IX mimic has been characterized kinetically using (18)O-exchange and structurally using X-ray crystallography, alone and in complex with five CA sulfonamide-based inhibitors (acetazolamide, benzolamide, chlorzolamide, ethoxzolamide, and methazolamide), and compared to CA II. This structural information has been evaluated by both inhibition studies and in vitro cytotoxicity assays and shows a correlated structure-activity relationship. Kinetic and structural studies of CA II and CA IX mimic reveal chlorzolamide to be a more potent inhibitor of CA IX, inducing an active-site conformational change upon binding. Additionally, chlorzolamide appears to be cytotoxic to prostate cancer cells. This preliminary study demonstrates that the CA IX mimic may provide a useful model to design more isozyme-specific CA IX inhibitors, which may lead to development of new therapeutic treatments of some cancers.

DrugBank Data that Cites this Article

Polypeptides

Name	UniProt ID
Carbonic anhydrase 2	P00918	Details

Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
5-(2-chlorophenyl)-1,3,4-thiadiazole-2-sulfonamide	Carbonic anhydrase 2	Ki (nM)	2	N/A	N/A	Details
Acetazolamide	Carbonic anhydrase 2	Ki (nM)	10.1	N/A	N/A	Details
Ethoxzolamide	Carbonic anhydrase 2	Ki (nM)	<1	N/A	N/A	Details