Carbonic Anhydrase: Structure, Catalytic Versatility, and Inhibition

Pocker, Y.; Sarkanen, Simo

doi:10.1002/9780470122921.ch3

Cited by 54 publications

(36 citation statements)

References 250 publications

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“…40,240 This conical cavity is visible at the centers of parts A and C of Figure 5. The catalytic Zn II ion, Zn262, lies at the apex of the cone near the center of the protein and is coordinated in a distorted tetrahedral arrangement to a hydroxide ion or water molecule (water263) and three histidine residues, His94, His96, and His119, which are located on the central β-sheet-His94 and His96 on βD and His119 on βE.…”

Section: Structure Of the Binding Cavity-mentioning

confidence: 99%

“…Although other activities may not be relevant to its principal biological role, CA can catalyze the hydration of aryl and aliphatic aldehydes [37][38][39] and the hydrolysis of a wide variety of esters in vitro. 40,41 Bovine CA II (BCA II) resolves mixtures of racemic N-acetylamino acids by selectively hydrolyzing the ester of only one enantiomer. 42 Human CA I and CA II (HCA I and HCA II) catalyze the hydrolysis of 1-fluoro-2,4-dinitrobenzene 43 and sulfonyl chlorides.…”

Section: Overview Of Enzymatic Activitymentioning

confidence: 99%

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Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

et al. 2008

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I. Introduction to Carbonic Anhydrase (CA) and to the Review 948 1. Introduction: Overview of CA as a Model 948 1.1. Value of Models 950 1.2. Objectives and Scope of the Review 950 2. Overview of Enzymatic Activity 950 3. Medical Relevance 951 II. Structure and Structure−Function Relationships of CA 953 4. Global and Active-Site Structure 953 4.1. Structure of Isoforms 953 4.2. Isolation and Purification 954 4.3. Crystallization 954 4.4. Structures Determined by X-ray Crystallography and NMR 955 4.4.1. Structures Determined by X-ray Crystallography 955 4.4.2. Structure Determined by NMR 955 4.5. Global Structural Features 963 4.6. Structure of the Binding Cavity 964 4.7. Zn II -Bound Water 965 5. Metalloenzyme Variants 966 6. Structure−Function Relationships in the Catalytic Active Site of CA 968 6.1. Effects of Ligands Directly Bound to Zn II 968 6.2. Effects of Indirect Ligands 969 7. Physical-Organic Models of the Active Site of CA 969 III. Using CA as a Model to Study Protein−Ligand Binding 970 8. Assays for Measuring Thermodynamic and Kinetic Parameters for Binding of Substrates and Inhibitors 970 8.1. Overview 970 8.

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Section: Structure Of the Binding Cavity-mentioning

confidence: 99%

Section: Overview Of Enzymatic Activitymentioning

confidence: 99%

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

et al. 2008

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“…The fivemembered ring of thioxolone also contains both ester and thioester groups, which could mimic the transition state for the CA-catalyzed esterase reaction. Furthermore, either or both of the ester and thioester bonds could function as substrates for the well-known nonphysiological esterase activity of CA II, (49,50) which involves a zinc-hydroxide mechanism (49)(50)(51)(52)(60)(61)(62). Here, we describe a detailed initial investigation of the thioxolone inhibition mechanism, with the aim of gaining a more detailed understanding of this novel class of CA inhibitor, and present a set of structure-activity relationship (SAR) data for a number of structural analogues.…”

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confidence: 99%

“…We recently performed a screening study of a model library of 960 structurally diverse, biologically active compounds against human CA II, using a well-known esterase assay with 4-nitrophenyl acetate (4-NPA) (1,(49)(50)(51)(52). This screen yielded a number of CA inhibitors, including thioxolone (6-hydroxy-1,3-benzoxathiol-2-one), a biologically active compound not previously described as a CA inhibitor (compound 1, Table 1).…”

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confidence: 99%

Inhibition of Carbonic Anhydrase II by Thioxolone: A Mechanistic and Structural Study

et al. 2008

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This paper examines the functional mechanism of thioxolone, a compound recently identified as a weak inhibitor of human carbonic anhydrase II by Iyer et al. (2006) J. Biomol. Screening 11, 782-791. Thioxolone lacks sulfonamide, sulfamate, or hydroxamate functional groups that are typically found in therapeutic carbonic anhydrase (CA) inhibitors, such as acetazolamide. Analytical chemistry and biochemical methods were used to investigate the fate of thioxolone upon binding to CA II, including Michaelis-Menten kinetics of 4-nitrophenyl acetate esterase cleavage, liquid chromatography-mass spectrometry (LC-MS), oxygen-18 isotope exchange studies, and X-ray crystallography. Thioxolone is proposed to be a prodrug inhibitor that is cleaved via a CA II zinc-hydroxide mechanism known to catalyze the hydrolysis of esters. When thioxolone binds in the active site of CA II, it is cleaved and forms 4-mercaptobenzene-1,3-diol via the intermediate S- (2,4-thiophenyl)hydrogen thiocarbonate. The esterase cleavage product binds to the zinc active site via the thiol group and is therefore the active CA inhibitor, while the intermediate is located at the rim of the active-site cavity. The time-dependence of this inhibition reaction was investigated in detail. Because this type of prodrug inhibitor mechanism depends on cleavage of ester bonds, this class of inhibitors may have advantages over sulfonamides in determining isozyme specificity. A preliminary structure-activity relationship study with a series of structural analogues of thioxolone yielded similar estimates of inhibition constants for most compounds, although two compounds with bromine groups at the C1 carbon of thioxolone were not inhibitory, suggesting a possible steric effect.

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“…Carbonic anhydrase (CA) is a zinc metalloenzyme catalyzing the interconversion of carbon dioxide and bicarbonate as well as the hydrolysis of certain esters and the hydration of aldehydes (Pocker and Sarkanen, 1978). Seven distinct isoforms, differing in their catalytic properties and their sensitivity to various inhibitors, have been found in mammals (Tashian, 1989).…”

mentioning

confidence: 99%

Catalytic and Inhibitor‐Binding Properties of Some Active‐Site Mutants of Human Carbonic Anhydrase I

Engstrand

Jonsson

Lindskog

1995

European Journal of Biochemistry

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Three isozyme-specific residues in the active site of human carbonic anhydrase I, Va162, His67, and His200, have been changed by site-directed mutagenesis to their counterparts in human carbonic anhydrase 11, Asn62, Asn67, and Thr200. A double mutant, containing Asn62 and Asn67, and a triple mutant, containing all three alterations, were also produced. The rates of CO, hydration and ester hydrolysis catalyzed by these mutants, the inhibition of these enzymes by the anions, SCN-, and I-, and the binding of the sulfonamide inhibitors, dansylamide and MK-417 (a thienothiopyran-2-sulfonamide) have been measured. The results suggest that the effect of His200 in isozyme I is to prolong the lifetime of the enzyme-bicarbonate complex and to increase the pK, of the catalytic group, a zinc-coordinated water molecule. For isozyme I, Val62 and His67 might interfere with the function of a proton 'shuttle' group in the active site, thus maintaining the buffer specificity of a compulsory proton-transfer step. The single mutations have small effects on anion binding. Only the triple mutant has anion-binding properties resembling those of isozyme 11. All mutants show altered sulfonamide-binding properties. In particular, the binding specificity is affected. While wild-type isozyme I binds dansylamide SO times more strongly than MK-417, the triple mutant shows a reversed selectivity and binds MK-417 nearly SO times more strongly than dansylamide.

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Carbonic Anhydrase: Structure, Catalytic Versatility, and Inhibition

Cited by 54 publications

References 250 publications

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

Carbonic Anhydrase as a Model for Biophysical and Physical-Organic Studies of Proteins and Protein−Ligand Binding

Inhibition of Carbonic Anhydrase II by Thioxolone: A Mechanistic and Structural Study

Catalytic and Inhibitor‐Binding Properties of Some Active‐Site Mutants of Human Carbonic Anhydrase I

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