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

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


An NAD(+)-dependent glutamate dehydrogenase (GDH; EC 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 alpha-ketoglutarate (apparent K(m) of 2.33 and 0.71 mM, respectively) and a low affinity for glutamate (apparent K(m) 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)113-21
Number of pages9
JournalFEMS Microbiology Letters
Issue number2
Publication statusPrint publication - 15 Jun 2005
Externally publishedYes


  • Amino Acid Sequence
  • Ammonia/metabolism
  • Animals
  • Bacteroides/genetics
  • Base Sequence
  • Ciliophora/enzymology
  • Cloning, Molecular
  • DNA, Protozoan/chemistry
  • Escherichia coli/genetics
  • Gene Expression Regulation
  • Gene Transfer, Horizontal
  • Genes, Protozoan
  • Glutamate Dehydrogenase/genetics
  • Glutamic Acid/metabolism
  • Ketoglutaric Acids/metabolism
  • Molecular Sequence Data
  • Phylogeny
  • RNA, Messenger/analysis
  • RNA, Protozoan/analysis
  • Recombinant Proteins/metabolism
  • Sequence Homology, Amino Acid
  • Substrate Specificity


Dive into the research topics of 'An NAD(+)-dependent glutamate dehydrogenase cloned from the ruminal ciliate protozoan, Entodinium caudatum'. Together they form a unique fingerprint.

Cite this