Open AccessAn NAD + ‐dependent glutamate dehydrogenase cloned from the ruminal ciliate protozoan, Entodinium caudatum
Author(s) -
Newbold C. James,
McEwan Neil R.,
Calza Roger E.,
Chareyron Emilie N.,
Duval Stéphane M.,
Eschenlauer Sylvain C.P.,
McIntosh Freda M.,
Nelson Nancy,
Travis Anthony J.,
Wallace R. John
Publication year - 2005
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2005.04.034
Subject(s) - glutamate dehydrogenase , biology , rumen , biochemistry , bacteria , escherichia coli , microbiology and biotechnology , nad+ kinase , enzyme , ciliate , gene , glutamate receptor , fermentation , genetics , receptor
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 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.