Paraoxon, 4-nitrophenyl phosphate and acetate are substrates of α- but not of β-, γ- and ζ-carbonic anhydrases

Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to alpha-, beta-, gamma- and zeta-classes and from various organisms, ranging from the bacteria, archaea to eukarya domains, were investigated for their esterase/phosphatase activity with 4-nitrophenyl acetate, 4-nitrophenyl phosphate and paraoxon as substrates. Only alpha-CAs showed esterase/phosphatase activity, whereas enzymes belonging to the beta-, gamma- and zeta-classes were completely devoid of such activity. Paraoxon, the metabolite of the organophosphorus insecticide parathione, was a much better substrate for several human/murine alpha-CA isoforms (CA I, II and XIII), with k(cat)/K-M in the range of 2681.6-4474.9 M (1) s (1), compared to 4-nitrophenyl phosphate (k(cat)/K-M of 14.9-1374.4 M (1) s (1)). (C) 2010 Elsevier Ltd. All rights reserved.