Crystal structure of human carbonic anhydrase XIII and its complex with the inhibitor acetazolamide

Abstract

The cytosolic isoform XIII is a recently discovered member of the human carbonic anhydrase (hCA, EC 4.2.1.1) family. It is selectively expressed among other tissues in the reproductive organs, where it may control pH and ion balance regulation, ensuring thus proper fertilization conditions. The authors report here the X-ray crystallographic structure of this isozyme in the unbound state and in complex with a classical sulfonamide inhibitor, namely acetazolamide. A detailed comparison of the obtained structural data with those already reported for other CA isozymes provides novel insights into the catalytic properties of the members of this protein family. On the basis of the inhibitory properties of acetazolamide against various cytosolic/transmembrane isoforms and the structural differences detected within the active site of the various CA isoforms, further prospects for the design of isozyme-specific CA inhibitors are here proposed.

Salts of 5-amino-2-sulfonamide-1,3,4-thiadiazole, a structural and analog of acetazolamide, show interesting carbonic anhydrase inhibitory properties, diuretic, and anticonvulsant action

“…These results show that although the solubility in water is improved for Hats by salt formation, the interaction of the sulfonamide with the active site of the enzyme is weaker (than for acetazolamide) probably due to the fact that the acetamido moiety present in the drug allows the stabilization of the adduct through additional interactions in which Hats cannot participate. This is consistent with the X-ray crystal structures, in which the deprotonated sulfonamido group appears bound to the Zn(II) ion from the enzyme active site 7,44,45 . In previous studies, it was found that by inhibiting CAs from bacterial or other pathogens, a growth inhibition of the studied micro-organisms occurred 37,45,46 .…”

“…The uncatalyzed rates were determined in the same manner and subtracted from the total observed rates. Enzyme concentrations in the assay system were in the range of 10 nM for all the enzymes considered in the present study, which have been obtained as recombinant proteins, in-house, as reported earlier [43][44][45][46][47][48] .…”

“…AZA, a well-known CAI, was used as a standard drug for comparison ( Table 5). As in other CAs inhibition assays with sulfonamides and their metal complexes, phenols and thiophenols, the enzymes were incubated for 10-15 min with test compounds for allowing the formation of the enzyme-inhibitor adduct [41][42][43][44][45]49,50 . Working under similar conditions, Hats salts inhibited both hCAs and micro-organisms CAs in the micromolar concentration range, although they exhibited a weaker inhibitory power compared with AZA (Table 5).…”

Synthesis and carbonic anhydrase isoenzymes I and II inhibitory effects of novel benzylamine derivatives

“…Human erythrocyte CA I isoenzyme was purified, 312.2-fold with a specific activity of 626 EU/mg and overall yield of 60.7%; CA II isoenzyme was purified, 296-fold with a specific activity of 594 EU/mg and an overall yield of 44.1%. We report here the first study on the inhibitory effects of novel benzylamine derivatives (22)(23)(24)(25)(26)(27)(28) on the esterase activity of hCA I and II. The inhibitor concentrations that caused 50% inhibition (IC 50 ) were determined from activity versus (%)-[benzylamines] plots and the K i values were calculated from the Lineweaver-Burk plots ( Table 2).…”

“…Recently, numerous structural studies have provided a scientific basis for the rational drug design of more selective enzyme inhibitors 20 . Nevertheless, although X-ray crystal structures are available for the majority of the 12 catalytically active members of the hCA family [21][22][23] , most of the reported complexes with inhibitors regards just isozyme II, which is the most thoroughly characterized CA isoform 2 . In the current research, the first synthesis of a number of novel diarylmethylamine hydrochloride salts 22-25 and their sulfonamide derivatives 26-28 was studied.…”