Carbonic Anhydrase Activators. Activation of Isozymes I, II, IV, VA, VII, and XIV withL- andD-Histidine and Crystallographic Analysis of Their Adducts with Isoform II: Engineering Proton-Transfer Processes within the Active Site of an Enzyme

Biocalcite and Carbonic Acid Activators

Based on evolution of biomineralizing systems and energetic considerations, there is now compelling evidence that enzymes play a driving role in the formation of the inorganic skeletons from the simplest animals, the sponges, up to humans. Focusing on skeletons based on calcium minerals, the principle enzymes involved are the carbonic anhydrase (formation of the calcium carbonate-based skeletons of many invertebrates like the calcareous sponges, as well as deposition of the calcium carbonate bioseeds during human bone formation) and the alkaline phosphatase (providing the phosphate for bone calcium phosphate-hydroxyapatite formation). These two enzymes, both being involved in human bone formation, open novel not yet exploited targets for pharmacological intervention of human bone diseases like osteoporosis, using compounds that act as activators of these enzymes. This chapter focuses on carbonic anhydrases of biomedical interest and the search for potential activators of these enzymes, was well as the interplay between carbonic anhydrase-mediated calcium carbonate bioseed synthesis and metabolism of energy-rich inorganic polyphosphates. Beyond that, the combination of the two metabolic products, calcium carbonate and calcium-polyphosphate, if applied in an amorphous form, turned out to provide the basis for a new generation of scaffold materials for bone tissue engineering and repair that are, for the first time, morphogenetically active.

Burkholderia pseudomallei γ-carbonic anhydrase is strongly activated by amino acids and amines

Activation of the γ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei (BpsγCA) with a series of natural and non-natural amino acids and aromatic/heterocyclic amines has been investigated. The best BpsγCA activators were d-His, l-DOPA, d-Trp, 4-amino-l-Phe, dopamine, 2-(2-aminoethyl)pyridine, 2-aminoethyl-piparazine/morpholine and l-adrenaline, which showed activation constants ranging between 9 and 86nM. The least effective activators were l-His, l-Phe and 2-pyridyl-methylamine, with K_As in the range of 1.73-24.7μM. As little is known about the role of γ-CAs in the lifecycle and virulence of this saprophytic bacterium, this study may shed some light on such phenomena. This is the first CA activation study of a γ-CA from a pathogenic bacterium, the only other such study being on the enzyme discovered in the archaeon Methanosarcina thermophila, Cam.

Tracking solvent and protein movement during CO2 release in carbonic anhydrase II crystals

Carbonic anhydrases are mostly zinc metalloenzymes that catalyze the reversible hydration/dehydration of CO2/HCO3 (-) Previously, the X-ray crystal structures of CO2-bound holo (zinc-bound) and apo (zinc-free) human carbonic anhydrase IIs (hCA IIs) were captured at high resolution. Here, we present sequential timeframe structures of holo- [T = 0 s (CO2-bound), 50 s, 3 min, 10 min, 25 min, and 1 h] and apo-hCA IIs [T = 0 s, 50 s, 3 min, and 10 min] during the "slow" release of CO2 Two active site waters, WDW (deep water) and WDW' (this study), replace the vacated space created on CO2 release, and another water, WI (intermediate water), is seen to translocate to the proton wire position W1. In addition, on the rim of the active site pocket, a water W2' (this study), in close proximity to residue His64 and W2, gradually exits the active site, whereas His64 concurrently rotates from pointing away ("out") to pointing toward ("in") active site rotameric conformation. This study provides for the first time, to our knowledge, structural "snapshots" of hCA II intermediate states during the formation of the His64-mediated proton wire that is induced as CO2 is released. Comparison of the holo- and apo-hCA II structures shows that the solvent network rearrangements require the presence of the zinc ion.

The effect of erythrocyte membranes from diabetic and hypercholesterolemic individuals on human carbonic anhydrase II activity

CONTEXT

Erythrocyte membranes regulate many enzyme activities, including carbonic anhydrase II (CA II). Membrane fluidity is associated with alterations in protein function and protein-protein interactions.

OBJECTIVE

The purpose of this study was to show the human CA II (hCA II) activity regulation by human erythrocyte membranes from diabetic and hypercholesterolemic subjects.

MATERIALS AND METHODS

Erythrocyte membranes were obtained from diabetic, hypercholesterolemic, and healthy subjects. hCA II activity was measured using the electrometric method.

RESULTS

hCA II activity was increased in vitro by membranes from both diabetic and hypercholesterolemic patients, with hypercholesterolemic membranes exhibiting a greater increase.

CONCLUSION

Changes in membrane composition may affect the erythrocyte membranes' capacity to increase in vitro hCA II activity.

How many carbonic anhydrase inhibition mechanisms exist?

Six genetic families of the enzyme carbonic anhydrase (CA, EC 4.2.1.1) were described to date. Inhibition of CAs has pharmacologic applications in the field of antiglaucoma, anticonvulsant, anticancer, and anti-infective agents. New classes of CA inhibitors (CAIs) were described in the last decade with enzyme inhibition mechanisms differing considerably from the classical inhibitors of the sulfonamide or anion type. Five different CA inhibition mechanisms are known: (i) the zinc binders coordinate to the catalytically crucial Zn(II) ion from the enzyme active site, with the metal in tetrahedral or trigonal bipyramidal geometries. Sulfonamides and their isosters, most anions, dithiocarbamates and their isosters, carboxylates, and hydroxamates bind in this way; (ii) inhibitors that anchor to the zinc-coordinated water molecule/hydroxide ion (phenols, carboxylates, polyamines, 2-thioxocoumarins, sulfocoumarins); (iii) inhibitors which occlude the entrance to the active site cavity (coumarins and their isosters), this binding site coinciding with that where CA activators bind; (iv) compounds which bind out of the active site cavity (a carboxylic acid derivative was seen to inhibit CA in this manner), and (v) compounds for which the inhibition mechanism is not known, among which the secondary/tertiary sulfonamides as well as imatinib/nilotinib are the most investigated examples. As CAIs are used clinically in many pathologies, with a sulfonamide inhibitor (SLC-0111) in Phase I clinical trials for the management of metastatic solid tumors, this review updates the recent findings in the field which may be useful for a structure-based drug design approach of more selective/potent modulators of the activity of these enzymes.

Inhibition of mammalian carbonic anhydrase isoforms I-XIV with a series of phenolic acid esters

A series of phenolic acid esters incorporating caffeic, ferulic, and p-coumaric acid, and benzyl, m/p-hydroxyphenethyl- as well as p-hydroxy-phenethoxy-phenethyl moieties were investigated for their inhibitory effects against the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Many of the mammalian isozymes of human (h) or murine (m) origin, hCA I-hCA XII, mCA XIII and hCA XIV, were inhibited in the submicromolar range by these derivatives (with KIs of 0.31-1.03 μM against hCA VA, VB, VI, VII, IX and XIV). The off-target, highly abundant isoforms hCA I and II, as well as hCA III, IV and XII were poorly inhibited by many of these esters, although the original phenolic acids were micromolar inhibitors. These phenols, like others investigated earlier, possess a CA inhibition mechanism distinct of the sulfonamides/sulfamates, clinically used drugs for the treatment of a multitude of pathologies, but with severe side effects due to hCA I/II inhibition. Unlike the sulfonamides, which bind to the catalytic zinc ion, phenols are anchored at the Zn(II)-coordinated water molecule, binding more externally within the active site cavity, and making contacts with amino acid residues at the entrance of the active site. As this is the region with the highest variability between the many CA isozymes found in mammals, this class of compounds shows isoform-selective inhibitory profiles, which may be exploited for obtaining pharmacological agents with less side effects compared to other classes of inhibitors.

Dendrimers incorporating benzenesulfonamide moieties strongly inhibit carbonic anhydrase isoforms I-XIV

As extension of our previous study herein we report a comprehensive investigation of poly(amidoamine) (PAMAM) dendrimers as modulators of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms I-XIV. Interestingly inhibitory activity was observed for the non-functionalized dendrimers against the hCA I, VII, IX, XII and XIV isoforms, whereas activation properties were reported only for the cytosolic abundant hCA II. Highly efficient inhibitory action against many isoforms having medicinal chemistry applications, such as hCA II, V, VII, IX, XII and XIV, was observed for the PAMAM functionalized counterparts bearing 4, 8, 16 and 32 benzenesulfonamide moieties. Possible applications of dendrimer-CA inhibitors as therapeutic/diagnostic agents are envisaged.

Exploring carbonic anhydrase inhibition with multimeric coumarins displayed on a fullerene scaffold

This study reports the first synthesis of multimeric suicide inhibitors of carbonic anhydrases.

Ethylene bis-imidazoles are highly potent and selective activators for isozymes VA and VII of carbonic anhydrase, with a potential nootropic effect

A series of ethylene bis-imidazoles was synthesized via a novel microwave-mediated synthesis. Biological testing on eight isozymes of carbonic anhydrase (CA) present in the human brain revealed compounds with nanomolar potency against CA VA and CA VII, also displaying excellent selectivity against other CA isozymes present in this organ.

Dominant behaviours in the expression of human carbonic anhydrase hCA I activity

Dynamic deconvolution ofDCLsof inhibitors (CAIs) and activators (CAAs) of hCA I show that the inhibitory effects dominate over the activating ones.

Carbonic anhydrase inhibitors drug design

Inhibition of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) has pharmacologic applications in the field of antiglaucoma, anticonvulsant, antiobesity, and anticancer agents but is also emerging for designing anti-infectives (antifungal and antibacterial agents) with a novel mechanism of action. As a consequence, the drug design of CA inhibitors (CAIs) is a very dynamic field. Sulfonamides and their isosteres (sulfamates/sulfamides) constitute the main class of CAIs which bind to the metal ion in the enzyme active site. Recently the dithiocarbamates, possessing a similar mechanism of action, were reported as a new class of inhibitors. Other families of CAIs possess a distinct mechanism of action: phenols, polyamines, some carboxylates, and sulfocoumarins anchor to the zinc-coordinated water molecule. Coumarins and five/six-membered lactones are prodrug inhibitors, binding in hydrolyzed form at the entrance of the active site cavity. Novel drug design strategies have been reported principally based on the tail approach for obtaining all these types of CAIs, which exploit more external binding regions within the enzyme active site (in addition to coordination to the metal ion), leading thus to isoform-selective compounds. Sugar-based tails as well as click chemistry were the most fruitful developments of the tail approach. Promising compounds that inhibit CAs from bacterial and fungal pathogens, of the dithiocarbamate, phenol and carboxylate types have also been reported.

Synthesis and carbonic anhydrase inhibitory properties of sulfamides structurally related to dopamine

A series of novel sulfamides incorporating the dopamine scaffold were synthesized. Reaction of amines and tert-butyl-alcohol/benzyl alcohol in the presence of chlorosulfonyl isocyanate (CSI) afforded sulfamoyl carbamates, which were converted to the title compounds by treatment with trifluoroacetic acid or by palladium-catalyzed hydrogenolysis. Inhibition of six α-carbonic anhydrases (CAs, EC 4.2.1.1), that is, CA I, CA II, CA VA, CA IX, CA XII and CA XIV, and two β-CAs from Candida glabrata (CgCA) and Mycobacterium tuberculosis (Rv3588) with these sulfamides was investigated. All CA isozymes were inhibited in the low micromolar to nanomolar range by the dopamine sulfamide analogues. K(i)s were in the range of 0.061-1.822 μM for CA I, 1.47-2.94 nM for CA II, 2.25-3.34 μM for CA VA, 0.041-0.37 μM for CA IX, 0.021-1.52 μM for CA XII, 0.007-0.219 μM for CA XIV, 0.35-5.31 μM for CgCA and 0.465-4.29 μM for Rv3588. The synthesized sulfamides may lead to inhibitors targeting medicinally relevant CA isoforms with potential applications as antiepileptic, antiobesity antitumor agents or anti-infective.

Tricyclic sulfonamides incorporating benzothiopyrano[4,3-c]pyrazole and pyridothiopyrano[4,3-c]pyrazole effectively inhibit α- and β-carbonic anhydrase: X-ray crystallography and solution investigations on 15 isoforms

Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous isozymes involved in crucial physiological and pathological events, representing the targets of inhibitors with several therapeutic applications. In this connection, we report a new class of carbonic anhydrase inhibitors, based on the thiopyrano-fused pyrazole scaffold to which a pendant 4-sulfamoylphenyl moiety was attached. The new sulfonamides 3a-e were designed as constrained analogues of celecoxib and valdecoxib. The most interesting feature of sulfonamides 3 was their predominantly strong inhibition of human (h) CA I and II, as well as those of the mycobacterial β-class enzymes (Rv1284, Rv3273, and Rv3588c), whereas their inhibitory action against hCA III, IV, VA, VB, VI, VII, IX, XII, XIII, and XIV was found to be at least 2 orders of magnitude lower. X-ray crystallography and structural superposition studies made it possible to explain the very distinct inhibition profile of the tricyclic sulfonamides, different from those of celecoxib and valdecoxib.

Structure, function and applications of carbonic anhydrase isozymes

The carbonic anhydrases enzymes (CAs, EC 4.2.1.1) are zinc containing metalloproteins, which efficiently catalyse the reversible conversion of carbon dioxide to bicarbonate and release proton. These enzymes are essentially important for biological system and play several important physiological and patho-physiological functions. There are 16 different alpha-carbonic anhydrase isoforms studied, differing widely in their cellular localization and biophysical properties. The catalytic domains of all CAs possess a conserved tertiary structure fold, with predominately β-strands. We performed an extensive analysis of all 16 mammalian CAs for its structure and function in order to establish a structure-function relationship. CAs have been a potential therapeutic target for many diseases. Sulfonamides are considered as a strong and specific inhibitor of CA, and are being used as diuretics, anti-glaucoma, anti-epileptic, anti-ulcer agents. Currently CA inhibitors are widely used as a drug for the treatment of neurological disorders, anti-glaucoma drugs, anti-cancer, or anti-obesity agents. Here we tried to emphasize how CAs can be used for drug discovery, design and screening. Furthermore, we discussed the role of CA in carbon capture, carbon sensor and metabolon. We hope this review provide many useful information on structure, function, mechanism, and applications of CAs in various discipline.

Carbonic anhydrase inhibitors and activators for novel therapeutic applications

Carbonic anhydrases (CAs, Enzyme Commission number 4.2.1.1) catalyze a simple but fundamental reaction, CO2 hydration to yield bicarbonate and protons. CAs belonging to the α-, β-, γ-, δ- and ζ-families are found in many organisms all over the phylogenetic tree and their inhibition/activation have been studied in detail, leading to various therapeutic applications. Inhibition of mammalian α-CAs is exploited by some diuretics, whereas antiglaucoma, anticonvulsant, anti-obesity, altitude sickness and anti-tumor drugs/diagnostic agents target various of the 15 isoforms described so far in these organisms. Activation of some CAs may also have applications in therapy. Bacterial and fungal β-CA inhibitors or nematode α-CA inhibitors have been described that may lead to novel classes of anti-infectives.

Carbonic anhydrase activators: gold nanoparticles coated with derivatized histamine, histidine, and carnosine show enhanced activatory effects on several mammalian isoforms

Lipoic acid moieties were attached to amine or amino acids showing activating properties against the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). The obtained lipoic acid conjugates of histamine, L-histidine methyl ester, and L-carnosine methyl ester were attached to gold nanoparticles (NPs) by reaction with Au(III) salts in reducing conditions. The CA activators (CAAs)-coated NPs showed low nanomolar activation (K(A)s of 1-9 nM) of relevant cytosolic, membrane-bound, mitochondrial, and transmembrane CA isoforms, such as CA I, II, IV, VA, VII, and XIV. These NPs also effectively activated CAs ex vivo, in whole blood experiments, with an increase of 200-280% of the CA activity. This is the first example of enzyme activation with nanoparticles and may lead to biomedical applications for conditions in which the CA activity is diminished, such as aging, Alzheimer's disease, or CA deficiency syndrome.

An inhibitor-like binding mode of a carbonic anhydrase activator within the active site of isoform II

The 2,4,6-trimethylpyridinium derivative of histamine is an effective activator of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). However, unlike other CA activators, which bind at the entrance of the active site cavity, an X-ray crystal structure of hCA II in complex with the 1-[2-(1H-imidazol-4-yl)-ethyl]-2,4,6-trimethylpyridinium salt evidenced a binding mode never observed before either for activators or inhibitors of this enzyme, with the 2,4,6-trimethylpyridinium ring pointing towards the metal ion deep within the enzyme cavity, and several strong hydrophobic interactions stabilizing the adduct. Indeed, incubation of the activator with the enzyme for several days leads to potent inhibitory effects. This is the first example of a CA activator which after a longer contact with the enzyme behaves as an inhibitor.

Bidentate Zinc chelators for alpha-carbonic anhydrases that produce a trigonal bipyramidal coordination geometry

A series of new zinc binding groups (ZBGs) has been evaluated kinetically on 13 carbonic anhydrase (CA) isoforms. The fragments show affinity for all isoforms with IC(50) values in the range of 2-11 microM. The crystal structure of hCA II in complex with one such fragment reveals a bidentate binding mode with a trigonal-bipyramidal coordination geometry at the Zn(2+) center. The fragment also interacts with Thr199 and Thr200 through hydrogen bonding and participates in a water network. Further development of this ZBG should increase the binding affinity leading to a structurally distinct and promising class of CA inhibitors.

Carbonic anhydrase activators. The first activation study of a coral secretory isoform with amino acids and amines

The activity of the coral Stylophora pystillata secretory carbonic anhydrase STPCA has been tested in presence of amino acids and amines. All the investigated compounds showed a positive, activating effect on k(cat) and have been separated in weak (K(A) in the range of 21-126 microM), medium (10.1-19 microM) and strong enzyme activators (K(A) of 0.18-3.21 microM). D-DOPA was found to be the best coral enzyme activator, with an activation constant K(A) of 0.18 microM. This enhancement of STPCA activity, as well as previous enzyme inhibition results, might now be tested on living organisms to better understand the role played by these enzymes in the coral calcification processes.

Carbonic anhydrase activators: activation of the beta-carbonic anhydrases from the pathogenic fungi Candida albicans and Cryptococcus neoformans with amines and amino acids

The proteins encoded by the Nce103 genes of Candida albicans and Cryptococcus neoformans are catalytically active beta-carbonic anhydrases (CAs, EC 4.2.1.1) playing various roles in the life cycle of these fungal pathogens, such as CO(2) sensing, regulation of capsule biosynthesis, filamentation, and adaptation of the organism to various pH and CO(2) conditions in various niches where the fungi grow. Here, we report the first activation study of these two enzymes, CaNce103 and Can2, respectively, with amines and amino acids. The C. albicans enzyme, CaNce103 was activated by amino acids such as L-/D-His, L-D-Trp, L-Tyr with K(A)s in the range of 19.5-46 microM. More effective activators were some amines such as histamine, dopamine, 2-aminoethyl-piperazine, and L-adrenaline (K(A)s of 13.2-18.5 microM). The best CaNce103 activators were L- and D-Dopa, with K(A)s of 0.96-2.5 microM. The C. neoformans enzyme, Can2, showed much lower propensity to be activated by all these amino acids and amines, which had activation constants in the range of 28.7-47.2 microM. The best Can2 activator was L-Trp. This study may help to better understand the catalytic/activation mechanisms of the beta-CAs and eventually to design CA activity modulators of such widespread enzymes in pathogenic fungi.

Carbonic anhydrase activators. Activation of the membrane-associated isoform XV with amino acids and amines

An activation study of the membrane-associated carbonic anhydrase (CA, EC 4.2.1.1) isoform XV with a series of natural and non-natural amino acids and aromatic/heterocyclic amines is reported. Murine CA XV was strongly activated by some amino acids (d-Phe, l-/d-DOPA, d-Trp, l-Tyr) and amines (dopamine, serotonin, l-adrenaline and 4-(2-aminoethyl)-morpholine) with activation constants in the range of 4.0-9.5muM. l-/d-His, l-Phe, histamine and several other heterocyclic amines showed less efficient activation (K(A)s in the range of 11.6-33.4muM). The activation profile of CA XV is quite different from that of the cytosolic isoforms CA I and II or the membrane-associated CA IV. All mammalian isoforms CA I-XV are thus characterized for their interaction with this set of amino acid and amine activators, some of which are biogenic amines or neurotransmitters present in sufficiently high amounts in various tissues for exerting significant biologic responses.

Carbonic anhydrase activators: activation of human isozymes I, II and IX with phenylsulfonylhydrazido l-histidine derivatives

Activation of the human carbonic anhydrase (CA, EC 4.2.1.1) isozymes I, II (cytosolic) and IX (transmembrane, tumor-associated isoform) with a series of arylsulfonylhydrazido-l-histidines incorporating 4-substituted-phenyl, pentafluorophenyl- and beta-naphthyl moieties was investigated. The compounds showed a weak hCA I activation profile, but were more efficient as hCA II and IX activators. The 4-iodophenyl-substituted derivative behaved as a strong and isozyme selective hCA II activator, with an activation constant of 0.21muM. This is the first isoform-selective, potent CA activator reported to date.

Carbonic anhydrase activators: activation of the beta-carbonic anhydrase Nce103 from the yeast Saccharomyces cerevisiae with amines and amino acids

The protein encoded by the Nce103 gene of Saccharomyces cerevisiae, a beta-carbonic anhydrase (CA, EC 4.2.1.1) designated as scCA, was investigated for its activation with amines and amino acids. scCA was poorly activated by amino acids such as l-/d-His, Phe, DOPA, Trp (K(A)s of 82-90 microM) and more effectively activated by amines such as histamine, dopamine, serotonin, pyridyl-alkylamines, aminoethyl-piperazine/morpholine (K(A)s of 10.2-21.3 microM). The best activator was l-adrenaline, with an activation constant of 0.95 microM. This study may help to better understand the catalytic/activation mechanisms of the beta-CAs and eventually to design modulators of CA activity for similar enzymes present in pathogenic fungi, such as Candida albicans and Cryptococcus neoformans.

Carbonic anhydrase activators: kinetic and X-ray crystallographic study for the interaction of D- and L-tryptophan with the mammalian isoforms I-XIV

An activation study of mammalian carbonic anhydrase (CA, EC 4.2.1.1) isoforms I-XIV with D- and L-tryptophan has been performed both by means of kinetic and X-ray crystallographic techniques. These compounds show a time dependent activity against isozyme CA II, with activation constants of 1.13 microM for L-Trp and 0.37 microM for D-Trp, respectively, after 24 h of incubation between enzyme and activator. The high resolution X-ray crystal structure of the hCA II-D-Trp adduct revealed the activator to bind in a totally unprecedented way to the enzyme active site as compared to histamine, L-/D-Phe, L-/D-His or L-adrenaline. D-Trp is anchored at the edge of the CA II active site entrance, strongly interacting with amino acid residues Asp130, Phe131 and Gly132 as well as with a loop of a second symmetry related protein molecule from the asymmetric unit, by means of hydrogen bonds and several weak van der Waals interactions involving Glu234, Gly235, Glu236 and Glu238. Thus, a second activator binding site (B) within the CA II cavity has been detected, where only D-Trp was shown so far to bind, in addition to the activator binding site A, in which histamine, L-/D-Phe, and L-/D-His are bound. These findings explain the strong affinity of D-Trp for CA II and may be useful for designing novel classes of CA activators by using this compound as lead molecule.

Carbonic anhydrases as drug targets

Carbonic anhydrases (CAs), the metalloenzymes that catalyze the conversion between carbon dioxide and bicarbonate, continue to be surprising targets, as many exciting new discoveries related to them emerge constantly. This is indeed unprecedented as these are quite "old" enzymes, which were discovered in 1933, and thoroughly investigated since then as drug targets. Furthermore, their inhibitors are in clinical use since the 50s. However, in the last years, a host of interesting reports were made regarding the catalytic/inhibition mechanism as well as isolation/characterization of new isozymes belonging to this family, as well as of CAs of non-vertebrate origin.

Carbonic anhydrases: novel therapeutic applications for inhibitors and activators

Carbonic anhydrases (CAs), a group of ubiquitously expressed metalloenzymes, are involved in numerous physiological and pathological processes, including gluconeogenesis, lipogenesis, ureagenesis, tumorigenicity and the growth and virulence of various pathogens. In addition to the established role of CA inhibitors (CAIs) as diuretics and antiglaucoma drugs, it has recently emerged that CAIs could have potential as novel anti-obesity, anticancer and anti-infective drugs. Furthermore, recent studies suggest that CA activation may provide a novel therapy for Alzheimer's disease. This article discusses the biological rationale for the novel uses of inhibitors or activators of CA activity in multiple diseases, and highlights progress in the development of specific modulators of the relevant CA isoforms, some of which are now being evaluated in clinical trials.

QSAR studies on the activation of the human carbonic anhydrase cytosolic isoforms I and II and secretory isozyme VI with amino acids and amines

The first QSAR study on the activation of the human secretory isoform of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), CA VI, with a series of amines and amino acids is reported. A large set of topological indices have been used to obtain several tri-/tetra-parametric models. We compared the CA VI activating QSAR models with those calculated for activation of the cytosolic human isozymes hCA I and hCA II. In addition, the effect of D- and L-amino acids as activators of hCA I, hCA II and of hCA VI as compared to those of structurally related biogenic amines was investigated for obtaining statistically significant and predictive QSAR equations. The obtained models are discussed using a variety of statistical parameters. The best models were obtained for hCA II activation, followed by hCA I, whereas the QSAR models for the activation of hCA VI were statistically weaker.