Archives of Microbiology

, Volume 183, Issue 5, pp 331–337

Purification and characterization of an NADH oxidase from extremely thermophilic anaerobic bacterium Thermotoga hypogea

Original Paper

DOI: 10.1007/s00203-005-0777-6

Cite this article as:
Yang, X. & Ma, K. Arch Microbiol (2005) 183: 331. doi:10.1007/s00203-005-0777-6

Abstract

Thermotoga hypogea is an extremely thermophilic anaerobic bacterium capable of growing at 90°C. It was found to be able to grow in the presence of micromolar molecular oxygen (O2). Activity of NADH oxidase was detected in the cell-free extract of T. hypogea, from which an NADH oxidase was purified to homogeneity. The purified enzyme was a homodimeric flavoprotein with a subunit of 50 kDa, revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It catalyzed the reduction of O2 to hydrogen peroxide (H2O2), specifically using NADH as electron donor. Its catalytic properties showed that the NADH oxidase had an apparent Vmax value of 37 μmol NADH oxidized min−1 mg−1 protein. Apparent Km values for NADH and O2 were determined to be 7.5 μM and 85 μM, respectively. The enzyme exhibited a pH optimum of 7.0 and temperature optimum above 85°C. The NADH-dependent peroxidase activity was also present in the cell-free extract, which could reduce H2O2 produced by the NADH oxidase to H2O. It seems possible that O2 can be reduced to H2O by the oxidase and peroxidase, but further investigation is required to conclude firmly if the purified NADH oxidase is part of an enzyme system that protects anaerobic T. hypogea from accidental exposure to O2.

Keywords

NADH oxidase Thermotoga hypogea Flavoprotein H2O2 Extreme thermophile Peroxidase 

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of BiologyUniversity of WaterlooWaterlooCanada

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