An NAD+-dependent glutamate dehydrogenase cloned from the ruminal ciliate protozoan, Entodinium caudatum

C. James Newbold, Neil R. McEwan, Roger E. Calza, Emilie N. Chareyron, Stéphane M. Duval, Sylvain C. P. Eschenlauer, Freda M. McIntosh, Nancy Nelson, Anthony J. Travis, R. John Wallace

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15 Citations (SciVal)

Abstract

An NAD+-dependent glutamate dehydrogenase (GDH; EC 1.4.1.24) was cloned from the ruminal ciliate protozoan, Entodinium caudatum. The gene had high sequence similarity to GDH genes from the Bacteroides (class) – a class of bacteria which is highly represented in the rumen. When expressed in Escherichia coli the enzyme had a high affinity for ammonia and α-ketoglutarate (apparent Km of 2.33 and 0.71 mM, respectively) and a low affinity for glutamate (apparent Km of 98 mM). GDH activity and GDH mRNA concentration were increased by incubating washed E. caudatum cells with ammonia and antibiotics. These results suggest that the GDH is an anabolic enzyme catalysing the assimilation of ammonia by E. caudatum in the rumen and that the gene was probably acquired by lateral gene transfer from a ruminal bacterium.
Original languageEnglish
Pages (from-to)113-121
Number of pages9
JournalFEMS Microbiology Letters
Volume247
Issue number2
DOIs
Publication statusPublished - 01 Jun 2005

Keywords

  • Ammonia uptake
  • Entodinium caudatum
  • Glutamate dehydrogenase
  • Protozoa
  • Rumen

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