tailieunhanh - Báo cáo khóa học: New activities of a catalytic antibody with a peroxidase activity

In order to estimate the size of the cavity remaining around the heme of the 3A3–microperoxidase 8 (MP8) hemo-abzyme,the formation of 3A3–MP8–Fe(II)-nitrosoalkane complexes upon oxidation of N-monosubstituted hydroxyl-amines was examined. This constituted a new reaction for hemoabzymes and is the first example of fully characterized Fe(II)–metabolite complexes of antibody–porphyrin. Also, via a comparison of the reactions with N-substituted hyd-roxylamines of various size and hydrophobicity,antibody 3A3 was confirmed to bring about a partial steric hindrance on the distal face of MP8 | Eur. J. Biochem. 271 1277-1283 2004 FEBS 2004 doi New activities of a catalytic antibody with a peroxidase activity Formation of Fe II RNO complexes and stereoselective oxidation of sulfides Remy Ricoux Edyta Lukowska Fabio Pezzotti and Jean-Pierre Mahy Laboratoire de Chimie Bioorganique et Bioinorganique Institut de Chimie Moléculaire et des Materiaux d Orsay Universite Paris-Sud XI Orsay France In order to estimate the size of the cavity remaining around the heme of the 3A3-microperoxidase 8 MP8 hemo-abzyme the lormaiion 4 3A3 MP8 Fe Ilj-nilrosoalkane complexes upon oxidation of N-monosubstituted hydroxylamines was examined. This constituted a new reaction for hemoabzymes and is the first example of fully characterized Fe II -metabolite complexes of antibody-porphyrin. Also via a comparison of the reactions with N-substituted hydroxylamines of various size and hydrophobicity antibody 3A3 was confirmed to bring about a partial steric hindrance on the distal face of MPP. Subsequently the ó t uncre of the antibody on the stereoselectivity of the S-oxidation of sulfides was examined. Our results showed that MPP alone and the antibody-MPP complex catalyze the oxidation of thioanisole by H2O2 and tert-butyl hydroperoxide folk wi ng a peroxidase-like two-step oxygen-transfer mechanism involving a radical-cation intermediate. The best system associating H2O2 as oxidant and 3A3-MPP as a catalyst m the presence of 5 tert-butyl alcohol led to toe steeoo-selective S-oxidation of thioanisole with a 45 enantiomeric excess in favour of the R isomer. This constitutes the highest enantiomeric excess reported to date for the oxidation of sulfides catalyzed by hemoabzymes. Keywords artificial hemoproteins abzymes nitrosoalcanes microperoxidase P S-oxidation. Catalytic antibodies with a metalloporphyrin cofactor or hemoabzymes tire not as fffictent a c ae i ory of c a y te as their natural hemoprotein counterparts. The hemoabzymes which display a .