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Nitrogen-15 Nuclear Magnetic Resonance Study of Benzenesulfonamide and Cyanate Binding to Carbonic Anhydrase

Kanamori, Keiko and Roberts, John D. (1983) Nitrogen-15 Nuclear Magnetic Resonance Study of Benzenesulfonamide and Cyanate Binding to Carbonic Anhydrase. Biochemistry, 22 (11). pp. 2658-2664. ISSN 0006-2960. doi:10.1021/bi00280a011.

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The binding of inhibitors, cyanate and benzenesulfonamide, to the active-site zinc of human carbonic anhydrase B was studied by ^(15)N nuclear magnetic resonance spectroscopy. The cyanate nitrogen resonance moved 34 ppm upfield on binding to the enzyme. The shielding is comparable to that reported for a zinc-isocyanate complex and strongly suggests complexation of cyanate to zinc through nitrogen. The proton-coupled ^(15)N resonance of the enzyme-bound benzenesulfonamide was a doublet. Hence, benzenesulfonamide is bound as C_6H_5SO_2NH-. The proton-decoupled ^(15)N resonance of the bound benzenesulfonamide was observed 17 ppm upfield of that of free enzenesulfonamide anion. A model ligand, 2-aminobenzenesulfonamide anion, undergoes binding of zinc through the sulfonamide nitrogen which results in an 11.8 ppm shielding of the ^(l5)N resonance. In contrast, N-( 2-aminophenyl)benzenesulfonamide, which is reported to bind zinc through an oxygen, has its sulfonamide nitrogen deshielded by 4.3 and 1.2 ppm on complexation of zinc to the neutral and anionic ligands, respectively. Thus, coordination to the nitrogen causes shielding and to the oxygen deshielding of the sulfonamide resonance. The observed shielding of the enzyme-bound sulfonamide resonance strongly suggests that benzenesulfonamide binds primarily to zinc through the sulfonamide nitrogen. The implications of these results for the high affinity of association of the inhibitor are discussed.

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Additional Information:© 1983 American Chemical Society. Received November 23, 1982. We thank Dr. Richard L. Weiss at the University of California, Los Angeles, for a critical reading of the manuscript and helpful suggestions. Supported by the National Science Foundation and by U.S. Public Health Service Grants GM-11072 and GM-31145 from the Division of General Medical Sciences.
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U.S. Public Health Service (USPHS)GM-11072
U.S. Public Health Service (USPHS)GM-31145
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Caltech Gates and Crellin Laboratories of Chemistry6760
Issue or Number:11
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Official Citation:Nitrogen-15 nuclear magnetic resonance study of benzenesulfonamide and cyanate binding to carbonic anhydrase Keiko Kanamori and John D. Roberts Biochemistry 1983 22 (11), 2658-2664 DOI: 10.1021/bi00280a011
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ID Code:60750
Deposited On:05 Oct 2015 18:17
Last Modified:10 Nov 2021 22:38

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