Human carbonic anhydrase II

Grtineberg S, Wendt B, Klebe G. Subnanomolar inhibitors from computer screening a model study using human carbonic anhydrase II. Angew Chem Int Ed Engl 2001 40 389-393 Angew Chem 2001 113 404-8. 

C. K. Tu, D. N. Silverman, C. Forsman, B. H. Jonsson, S. Lindskog, Role of Histidine 64 in the Catalytic Mechanism of Human Carbonic Anhydrase II Studied with a Site-Specific Mutant , Biochemistry 1989, 28, 7913-7918. 

Rowlett and Silverman used a Brpnsted plot to examine the interaction of external buffers with human carbonic anhydrase II. The buffers act as proton acceptors in the removal of the proton generated by the enzyme-catalyzed reaction. The Brpnsted plot displays a plateau at a value of about 10 for the catalytic rate... 

Human carbonic anhydrase II, found primarily in the erythrocyte, is the prototypical member of the family of carbonic anhydrases and has been extensively reviewed (Pocker and Sarkanen, 1978 Lindskog, 1983, 1986 Silverman and Lindskog, 1988). Within the erythrocyte carbonic anhydrase II hydrates CO2 to form bicarbonate ion plus a proton via tandem chemical processes (Silverman and Lindskog, 1988) (Scheme 2). Most of the carbon dioxide generated during the process of respiration requires this carbonic anhydrase Il-catalyzed event for transport out of the cell. The resultant protons of CO2 hydration are taken up by His-146)8, His-122a, and the amino terminus of the a subunits of the hemoglobin tetramer. As a reference. Scheme 3 outlines the interconversions... 

X-Ray crystallographic studies of native human carbonic anhydrase II have been reported at 2.0 A resolution (Eriksson et al, 1986, 1988a). Important active-site residues include Thr-199, Thr-200, Glu-106, His-64, Trp-209, Val-121, Val-143, the zinc ion (liganded by His-94, His-96, and His-119), and the zinc-bound hydroxide ion. A schematic view of the active site is found in Fig. 22. The globular protein has a molecular... 

Fig. 26. Electron density map, calculated with Fourier coefficients 2 Fo - [fj and phases calculated from the final model, of the hydrophobic pocket of the Val-14S- Tyr mutant of human carbonic anhydrase II (Alexander etai, 1991). This mutation nearly obliterates the pocket and results in a 10 -fold loss of activity (Fierke et ai, 1991).

Dorzolamide Hydrochloride is an inhibitor of human carbonic anhydrase II. The inhibition of carbonic anhydrase in the ciliary processes of the eye decreases the secretion of aqueous humor, with a resulting reduction in intraocular pressure. The drug is formulated as an ophthalmic solution, and administered topically as eyedrops. 

There are several types of -class CAs i.e., a-CA I-VII, reported in the literature, out of which the human carbonic anhydrase II (HCA II), the most extensively studied carbonic anhydrase, has an exceptionally high CO2 hydration rate and a wide tissue distribution 107). The HCA II comprises a single polypeptide chain with a molecular mass of 29.3 kDa and contains one catalytic zinc ion, coordinated to three histidine residues, His 94, His 96, and His 119. A tetrahedral coordination geometry around the metal center is completed with a water molecule, which forms a hydroxide ion with a pK value of 7.0 108). Quigley and co-workers 109,110) reported that the inhibition of the synthesis of HCO3 from CO2 and OH- reduces aqueous humor formation and lowers intra-ocular pressure, which is a major risk factor for primary open-angle glaucoma. 

Figure 10-5. The environment of the metal in a series of zinc metalloproteins. The proteins are (a) human carbonic anhydrase II, (b) thermolysin from Bacillus thermoproteolyticus, and (c) bovine pancreas carboxypeptidase. Each of these enzymes is, essentially, hydrolytic.

Figure 7.6 ESI of zinc metalloenzyme carbonic anhydrase, (a)-(c) under acidic denaturing conditions (d)-(f) native state conditions and (g) native state conditions with a specific inhibitor. Structure of entry (d) is Protein Data Bank ID IBN1. Boriack-Sjodin, P.A., Zeitlin, S., Chen, H.H., Crenshaw, L, Gross S., Dantanarayana, A., Delgado, P., May J.A., Dean, T., Christianson, D.W. Structural analysis of inhibitor binding to human carbonic anhydrase II. Protein Sciv 1998, 7, 2483-2489.

Vedani, A., Dunitz, J.D. Lone-pair Directionality of H-bond Potential Functions for Molecular Mechanics Calculations the Inhibition of Human Carbonic Anhydrase II by Sulfonamides. 

Avvaru BS et al (2010) A short, strong hydrogen bond in the active site of human carbonic anhydrase II. Biochem 49 249-251 PDBID 3KS3... 

Merz KM, Band L. Binding of azide to human carbonic anhydrase II the role electrostatic complementary plays in selecting the preferred resonance structure of azide. J Phys Chem 1996 100 17414-17420. 

Hammarstrom, P., Owenius, R., Martenson, L-G., Carlsson, U., and Lindgren, M. (2001) High resolution probing of local conformational change in proteins by the use of multiple labeling unfolding and self -assembly of human carbonic anhydrase II monitored by spin, fluorescent, and chemical reactivity probs, Biophys. J. 80, 2867-2885. 

Persson, M., Harbridge, J. R., Hammerstrom, P., Mitri, R., Ma rtenson, L-G., Carlson, U., Eaton, G., and Eaton, S. (2001) Comparison of electron paramagnetic resonance methods to determine distances between spin labels on human carbonic anhydrase II, Biophys. J. 80, 2886-2897. 

Vedani A, Dunitz JD (1985) Lone-pair directionality in hydrogen bond potential functions for molecular mechanics calculations. The inhibition of human carbonic anhydrase II by sulfonamides. J Am Chem Soc 107 7653-7658... 

Figure 5 H-bonds to the side-chain carboxyl group of Glull of human carbonic anhydrase II (pdb 1CA2 ). Structure prepared using DS ViewerPro 5.0 Accelrys Inc. San Diego, CA...

Heteronuclear Gradient-Enhanced NMR for the Study of 20-30kDa Proteins Application to Human Carbonic Anhydrase II... 

Carbonic anhydrases accelerate CO2 hydration dramatically. The most active enzymes, typified by human carbonic anhydrase II, hydrate CO2 at rates as high as k =10 s, or a million times a second. Fundamental physical processes such as diffusion and proton transfer ordinarily limit the rate of hydration, and so special strategies are required to attain such prodigious rates. 

To probe the capabilities of ab initio molecular dyuamics (AIMD) in describing enzymatic reactions, calculations have been carried out on two text-book examples, human carbonic anhydrase II and serine proteeise. As these are among the most theoretically and experimentally characterized enzymes, this work has provided a basis for subsequent applications in the field. 

D. Lu and G. A. Voth, Molecular dynamics simulations of human carbonic anhydrase II , Proteins 33, 119-134 1998. 

For the in vitro simulation the reagents of weak base B are triethylamine, iV-methy-morpholine, imidazole and 2,6-lutidine. In human carbonic anhydrase II a couple of water molecules connected to His 64 and Thr 199 through hydrogen bond may deprotonate a zinc-bound water molecule[17,... 

In conclusion, we have carried out the syntheses the complex coordinated by a single water molecule, [LZn(OH2)]2+ as a model complex of the active site in carbonic anhydrase. The geometry around zinc ion is similar to that of human carbonic anhydrase II. The deprotonation of coordinated water molecule was characterized by H, 13C NMR. It was demonstrated that the pATa of zinc-bound D2O is 8.6. The formation of hydrogen-carbonate complex, [LZn(0C02D)]+ as a product of reaction of [LZn(OD)]+ with CO2 gas has been revealed by NMR and i.r. studies. 

Eriksson, E. A., Jones, T. A. and Liljas, A. (1988) Refined Structure of Human Carbonic Anhydrase II at 2.0 A Resolution, Proteins Struct. Fund. Genet. 4, 274-282. 

Riccardi, D., Cui, Q. pK(a) analysis for the zinc-bound water in human carbonic anhydrase II Benchmark for "Multiscale" QM/MM simulations and mechanistic implications. J. Phys. Chem. A... 

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