Selected Publication:

Jakopitsch, C; Auer, M; Regelsberger, G; Jantschko, W; Furtmüller, PG; Rüker, F; Obinger, C.
(2003): The catalytic role of the distal site asparagine-histidine couple in catalase-peroxidases.
Eur J Biochem. 2003; 270(5):1006-1013 FullText FullText_BOKU

Abstract:

Catalase-peroxidases (KatGs) are unique in exhibiting an overwhelming catalase activity and a peroxidase activity of broad specificity. Similar to other peroxidases the distal histidine in KatGs forms a hydrogen bond with an adjacent conserved asparagine. To investigate the catalytic role(s) of this potential hydrogen bond in the bifunctional activity of KatGs, Asn153 in Synechocystis KatG was replaced with either Ala (Asn153-->Ala) or Asp (Asn153-->Asp). Both variants exhibit an overall peroxidase activity similar with wild-type KatG. Cyanide binding is monophasic, however, the second-order binding rates are reduced to 5.4% (Asn153-->Ala) and 9.5% (Asn153-->Asp) of the value of native KatG [(4.8 +/- 0.4) x 10(5) m(-1) .s(-1) at pH 7 and 15 degreesC]. The turnover number of catalase activity of Asn153-->Ala is 6% and that of Asn153-->Asp is 16.5% of wild-type activity. Stopped-flow analysis of the reaction of the ferric forms with H-2 O-2 suggest that exchange of Asn did not shift significantly the ratio of rates of H-2 O-2 -mediated compound I formation and reduction. Both rates seem to be reduced most probably because (a) the lower basicity of His123 hampers its function as acid-base catalyst and (b) Asn153 is part of an extended KatG-typical H-bond network, the integrity of which seems to be essential to provide optimal conditions for binding and oxidation of the second H-2 O-2 molecule necessary in the catalase reaction.

Authors BOKU Wien:

Auer Markus

Furtmüller Paul Georg

Jakopitsch Christa

Obinger Christian

Rüker Florian

Find related publications in this database (using NML MeSH Indexing)

Amino Acid Sequence -

Asparagine - chemistry

Base Sequence - chemistry

Catalase - chemistry

Catalysis - chemistry

Cyanides - metabolism

DNA Primers - metabolism

Histidine - chemistry

Kinetics - chemistry

Models, Molecular - chemistry

Molecular Sequence Data - chemistry

Peroxidase - chemistry

Sequence Homology, Amino Acid - chemistry

Spectrophotometry, Ultraviolet - chemistry

Find related publications in this database (Keywords)

catalase-peroxidase

Synechocystis PCC 6803

catalase activity

peroxidase activity

compound I

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