Extremophiles

, Volume 12, Issue 1, pp 89–96

The 2-oxoacid dehydrogenase multienzyme complex of Haloferax volcanii

Authors

  • Dina M. Al-Mailem
    • Department of Biological Sciences, Faculty of ScienceKuwait University
  • David W. Hough
    • Centre for Extremophile Research, Department of Biology and BiochemistryUniversity of Bath
    • Centre for Extremophile Research, Department of Biology and BiochemistryUniversity of Bath
Original Paper

DOI: 10.1007/s00792-007-0091-0

Cite this article as:
Al-Mailem, D.M., Hough, D.W. & Danson, M.J. Extremophiles (2008) 12: 89. doi:10.1007/s00792-007-0091-0

Abstract

Those aerobic archaea whose genomes have been sequenced possess four adjacent genes that, by sequence comparisons with bacteria and eukarya, appear to encode the component enzymes of a 2-oxoacid dehydrogenase multienzyme complex. However, no catalytic activity of any such complex has ever been detected in the archaea. In Thermoplasma acidophilum, evidence has been presented that the heterologously expressed recombinant enzyme possesses activity with the branched chain 2-oxoacids and, to a lesser extent, with pyruvate. In the current paper, we demonstrate that in Haloferax volcanii the four genes are transcribed as an operon in vivo. However, no functional complex or individual enzyme, except for the dihydrolipoamide dehydrogenase component, could be detected in this halophile grown on a variety of carbon sources. Dihydrolipoamide dehydrogenase is present at low catalytic activities, the level of which is increased three to fourfold when Haloferax volcanii is grown on the branched-chain amino acids valine, leucine and isoleucine.

Keywords

HaloferaxMultienzyme complex2-Oxoacid dehydrogenaseRT-PCRArchaea

Abbreviations

BCOADHC

Branched-chain 2-oxoacid dehydrogenase complex

DCPIP

2,6-Dichlorophenolindophenol

E1

2-Oxoacid decarboxylase

E2

Dihydrolipoyl acyl-transferase

E3

Dihydrolipoamide dehydrogenase

FOR

Ferredoxin oxidoreductase

Mr

Relative molecular mass

OADHC

2-Oxoacid dehydrogenase complex

OGDHC

2-Oxoglutarate dehydrogenase complex

PDHC

Pyruvate dehydrogenase complex

TPP

Thiamine pyrophosphate

Copyright information

© Springer 2007