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Manganese‐Substituted Carbonic Anhydrase as a New Peroxidase
Author(s) -
Okrasa Krzysztof,
Kazlauskas Romas J.
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501413
Subject(s) - chemistry , bicarbonate , peroxidase , carbonic anhydrase , manganese , active site , hydrogen peroxide , catalysis , zinc , myoglobin , horseradish peroxidase , enantioselective synthesis , medicinal chemistry , enzyme , stereochemistry , organic chemistry
Carbonic anhydrase is a zinc metalloenzyme that catalyzes the hydration of carbon dioxide to bicarbonate. Replacing the active‐site zinc with manganese yielded manganese‐substituted carbonic anhydrase (CA[Mn]), which shows peroxidase activity with a bicarbonate‐dependent mechanism. In the presence of bicarbonate and hydrogen peroxide, (CA[Mn]) catalyzed the efficient oxidation of o ‐dianisidine with k cat /K M =1.4×10 6 m −1 s −1 , which is comparable to that for horseradish peroxidase, k cat /K M =57×10 6 m −1 s −1 . CA[Mn] also catalyzed the moderately enantioselective epoxidation of olefins to epoxides ( E =5 for p ‐chlorostyrene) in the presence of an amino‐alcohol buffer, such as N,N ‐bis(2‐hydroxyethyl)‐2‐aminoethanesulfonic acid (BES). This enantioselectivity is similar to that for natural heme‐based peroxidases, but has the advantage that CA[Mn] avoids the formation of aldehyde side products. CA[Mn] degrades during the epoxidation limiting the yield of the epoxidations to <12 %. Replacement of active‐site residues Asn62, His64, Asn67, Gln92, or Thr200 with alanine by site‐directed mutagenesis decreased the enantioselectivity demonstrating that the active site controls the enantioselectivity of the epoxidation.