Studies of the Esterase Activity and the Anion Inhibition of Bovine Zinc and Cobalt Carbonic Anhydrases

Thorslund, A.; Lindskog, Sven

doi:10.1111/j.1432-1033.1967.tb19504.x

Cited by 158 publications

(121 citation statements)

References 34 publications

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“…The present data show, in addition, that two ionizing groups are important for the binding. One of these groups, with a p K of about 6.8, is very likely the same as the one involved in the pH-rate profile of the enzyme [16,22,25]. The second pK seems to be connected with the inhibitor.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, [22] and the slope gives ka = 7 x lo4 M-l -sec-l, irrespective of the type of inhibition. The other line in Fig.4 was obtained when the substrate was 7.0 mM CO,.…”

Section: Rates Of Sulfanilamide Inhibitionmentioning

confidence: 99%

“…Since the Michaelis constant, K m , is very large compared to the substrate concentration in this system [22], the inhibition can be treated as being noncompetitive. The inhibition constants, Kt , were thus evaluated using equation (I).…”

Section: Kinetic Measurementsmentioning

confidence: 99%

“…I n the usual procedure [22], buffer, enzyme and inhibitor were premixed to a total volume of 2.4 ml, and the reaction was initiated by the addition of 0.1 ml of 10 mM ester in acetone. The reaction was followed spectrophotometrically at the isosbestic wavelength for the phenol and the phenoxide, 348 mp.…”

Section: Kinetic Measurementsmentioning

confidence: 99%

“…The reaction was followed spectrophotometrically at the isosbestic wavelength for the phenol and the phenoxide, 348 mp. Initial rates were corrected for the rates of the nonenzymic reaction, and converted to molar units taking the difference between the molar absorbance coefficients of the phenol and the ester, A E = 5,150 M-1 * cm-l at 348 mp [22].…”

Section: Kinetic Measurementsmentioning

confidence: 99%

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On the Interaction of Bovine Cobalt Carbonic Anhydrase with Sulfonamides

Lindskog¹,

Thorslund²

1968

European Journal of Biochemistry

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1.The pHdependence of the inhibition of cobalt carbonic anhydrase by three different sulfonamides has been measured employing p-nitrophenyl acetate as substrate. The binding of these inhibitors is linked to two ionizing groups. One of these seems to be identical to the group in the enzyme previously shown to control the catalytic activity. The pK of the second group is characteristic for the individual inhibitor and agrees with pK-values obtained by titration of the sulfonamides. 2.Sulfanilamide and the anionic inhibitor, NO,-, appear to compete for one binding site on the enzyme.3. When the sulfanilamide inhibition of the C0,-hydration activity was studied by the stopped-flow method, some anomalous behavior was observed. From the initial part of the reactions, apparent noncompetitive inhibition was obtained. The rates increased over a short time period, however, to give essentially a competitive pattern. The results can be explained by assuming that the substrate and the inhibitor are competitive, but that equilibration is not immediately achieved duc to a comparatively slow rate of dissociation of the inhibitor from the enzyme.4. The apparent second order rate constant for the formation of the enzyme-sulfanilamide complex has been estimated as 7 x lo4 M-l sec-l a t pH 7.9 and 25". In the presence of CO, , the reaction is slower to an extent which is compatible with a competition for a common binding site. .A simple, though not unique, mechanism for the sulfonamide inhibition of bovine cobalt carbonic anhydrase, accounting for both rate and equilibrium data, implies the formation of the enzyme-inhibitor complex through a direct reaction of the ionized sulfonamide with the inactive, acid form of the enzyme.Aromatic and heterocyclic sulfonamides with an unsubstituted sulfonamide group constitute a class of powerful and highly specific inhibitors of carbonic anhydrase. Their physiological effects and their use as therapeutic agents have created a considerable interest in them in the field of molecular pharmacology [1,2]. I n addition, they are useful tools in current work on the elucidation of the structure and function of the enzyme. Whitney et al. [3] [B] that the metalion is required for the strong binding of acetazolamide (5-acetylamido-1,3,4-thiadiazole-2-sulfonamide). Furthermore, t,he sulfonamides have a pronounced effect on the structurc and intensity as well as the optical

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Section: Discussionmentioning

confidence: 99%

“…Thus, [22] and the slope gives ka = 7 x lo4 M-l -sec-l, irrespective of the type of inhibition. The other line in Fig.4 was obtained when the substrate was 7.0 mM CO,.…”

Section: Rates Of Sulfanilamide Inhibitionmentioning

confidence: 99%

Section: Kinetic Measurementsmentioning

confidence: 99%

Section: Kinetic Measurementsmentioning

confidence: 99%

Section: Kinetic Measurementsmentioning

confidence: 99%

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On the Interaction of Bovine Cobalt Carbonic Anhydrase with Sulfonamides

Lindskog¹,

Thorslund²

1968

European Journal of Biochemistry

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Carbonic Anhydrases (α‐Class)

Duda

McKenna

2004

Handbook of Metalloproteins

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Carbonic anhydrases (CAs) are zinc metalloenzymes that catalyze the hydration of carbon dioxide and the dehydration of bicarbonate: , a process that has physiological importance in respiration, acid–base homeostasis, photosynthesis, and biosynthetic pathways. The α‐class of CA (and the CA domains in more complex isoforms) is monomeric with a molecular weight of approximately 30 kDa. At present, 14 isoforms of the α‐class are known with varying tissue distributions and catalytic activity. The catalytic turnover number of CAs varies from the maximal rate of 10 6 s −1 for isozyme II to 10 3 s −1 for isozyme III. The central structural motif of the α‐CAs can be described as a 10‐stranded twisted β‐sheet, which is flanked by seven α‐helices. The active‐site cavity consists of a single zinc ion tetrahedrally coordinated by three histidine residues (His94, 96, and 119) and a bound water molecule. In most of the α‐CAs, the resultant proton formed by the dehydration reaction of bicarbonate is transferred to bulk solution through the formation of a proton wire, mediated by residue His64, that lies at the mouth of the active site. Known inhibitors of CAs have been shown to bind to the metal ion and displace the zinc‐bound water, whereas activators have been shown to bind at the entrance of the active site and mimic the characteristics of the proton‐shuttling residue His64.

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Carbonic Anhydrase: Structure, Catalytic Versatility, and Inhibition

Pocker

Sarkanen

1979

Advances in Enzymology - And Related Areas of Molecular Biology

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Studies of the Esterase Activity and the Anion Inhibition of Bovine Zinc and Cobalt Carbonic Anhydrases

Cited by 158 publications

References 34 publications

On the Interaction of Bovine Cobalt Carbonic Anhydrase with Sulfonamides

On the Interaction of Bovine Cobalt Carbonic Anhydrase with Sulfonamides

Carbonic Anhydrases (α‐Class)

Carbonic Anhydrase: Structure, Catalytic Versatility, and Inhibition

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