In:
Acta Crystallographica Section D Biological Crystallography, International Union of Crystallography (IUCr), Vol. 71, No. 12 ( 2015-12-01), p. 2449-2456
Abstract:
Carbonic anhydrase (CA) is a zinc enzyme that catalyzes the reversible conversion of carbon dioxide to bicarbonate (hydrogen carbonate) and a proton. CAs have been extensively investigated owing to their involvement in numerous physiological and pathological processes. Currently, CA inhibitors are widely used as antiglaucoma, anticancer and anti-obesity drugs and for the treatment of neurological disorders. Recently, the potential use of CA inhibitors to fight infections caused by protozoa, fungi and bacteria has emerged as a new research direction. In this article, the cloning and kinetic characterization of the β-CA from Vibrio cholerae (VchCAβ) are reported. The X-ray crystal structure of this new enzyme was solved at 1.9 Å resolution from a crystal that was perfectly merohedrally twinned, revealing a tetrameric type II β-CA with a closed active site in which the zinc is tetrahedrally coordinated to Cys42, Asp44, His98 and Cys101. The substrate bicarbonate was found bound in a noncatalytic binding pocket close to the zinc ion, as reported for a few other β-CAs, such as those from Escherichia coli and Haemophilus influenzae . At pH 8.3, the enzyme showed a significant catalytic activity for the physiological reaction of the hydration of CO 2 to bicarbonate and protons, with the following kinetic parameters: a k cat of 3.34 × 10 5 s −1 and a k cat / K m of 4.1 × 10 7 M −1 s −1 . The new enzyme, on the other hand, was poorly inhibited by acetazolamide ( K i of 4.5 µ M ). As this bacterial pathogen encodes at least three CAs, an α-CA, a β-CA and a γ-CA, these enzymes probably play an important role in the life cycle and pathogenicity of Vibrio , and it cannot be excluded that interference with their activity may be exploited therapeutically to obtain antibiotics with a different mechanism of action.
Type of Medium:
Online Resource
ISSN:
1399-0047
DOI:
10.1107/S1399004715018635
DOI:
10.1107/S1399004715018635/mn5102sup1.pdf
Language:
Unknown
Publisher:
International Union of Crystallography (IUCr)
Publication Date:
2015
detail.hit.zdb_id:
2020492-9
detail.hit.zdb_id:
2968623-4
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