TY - JOUR
T1 - Manganese-substituted carbonic anhydrase as a new peroxidase
AU - Okrasa, Krzysztof
AU - Kazlauskas, Romas J.
PY - 2006/2/8
Y1 - 2006/2/8
N2 - 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 kcat/KM = 1.4 × 10 6M-1S-1, which is comparable to that for horseradish peroxidase, kcat/KM = 57 × 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.
AB - 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 kcat/KM = 1.4 × 10 6M-1S-1, which is comparable to that for horseradish peroxidase, kcat/KM = 57 × 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.
KW - Carbonic anhydrase
KW - Enzyme catalysis
KW - Epoxidation
KW - Hydrogen peroxide
KW - Oxidation
UR - http://www.scopus.com/inward/record.url?scp=32944480336&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=32944480336&partnerID=8YFLogxK
U2 - 10.1002/chem.200501413
DO - 10.1002/chem.200501413
M3 - Article
C2 - 16416502
AN - SCOPUS:32944480336
SN - 0947-6539
VL - 12
SP - 1587
EP - 1596
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 6
ER -