Purification and inhibition studies with anions and sulfonamides of an α-carbonic anhydrase from the Antarctic seal Leptonychotes weddellii

Bioorg Med Chem. 2011 Mar 15;19(6):1847-51. doi: 10.1016/j.bmc.2011.02.015. Epub 2011 Feb 13.


A high activity α-carbonic anhydrase (CA, EC has been purified from various tissues of the Antarctic seal Leptonychotes weddellii. The new enzyme, denominated lwCA, has a catalytic activity for the physiologic CO(2) hydration to bicarbonate reaction, similar to that of the high activity human isoform hCA II, with a k(cat) of 1.1×10(6) s(-1), and a k(cat)/K(m) of 1.4×10(8) M(-1) s(-1). The enzyme was highly inhibited by cyanate, thiocyanate, cyanide, bicarbonate, carbonate, as well as sulfamide, sulfamate, phenylboronic/phenylarsonic acids (K(I)s in the range of 46-100 μM). Many clinically used sulfonamides, such as acetazolamide, methazolamide, dorzolamide, brinzolamide and benzolamide were low nanomolar inhibitors, with K(I)s in the range of 5.7-67 nM. Dichlorophenamide, zonisamide, saccharin and hydrochlorothiazide were weaker inhibitors, with K(I)s in the range of 513-5390 nM. The inhibition profile with anions and sulfonamides of the seal enzyme was rather different from those of the human isoforms hCA I and II. The high sensitivity to bicarbonate inhibition of lwCA, unlike that of the human enzymes, may reflect an evolutionary adaptation to the deep water, high CO(2) partial pressure and hypoxic conditions in which Weddell seals spend much of their life.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anions / chemistry*
  • Anions / pharmacology
  • Antarctic Regions
  • Carbonic Anhydrase I / antagonists & inhibitors
  • Carbonic Anhydrase I / metabolism
  • Carbonic Anhydrase II / antagonists & inhibitors
  • Carbonic Anhydrase II / metabolism
  • Carbonic Anhydrase Inhibitors / chemistry*
  • Carbonic Anhydrase Inhibitors / pharmacology
  • Carbonic Anhydrases / chemistry*
  • Carbonic Anhydrases / isolation & purification
  • Carbonic Anhydrases / metabolism
  • Humans
  • Protein Isoforms / antagonists & inhibitors
  • Protein Isoforms / metabolism
  • Seals, Earless / metabolism*
  • Sulfonamides / chemistry*
  • Sulfonamides / pharmacology


  • Anions
  • Carbonic Anhydrase Inhibitors
  • Protein Isoforms
  • Sulfonamides
  • Carbonic Anhydrase I
  • Carbonic Anhydrase II
  • Carbonic Anhydrases