title: The effect of L-alpha-amino-n-butyric acid on growth and production of extracellular isoleucine and valine by Eubacterium ruminantium and a related rumen isolate.
abstract: Two anaerobic rumen bacteria, Eubacterium ruminantium and a closely related isolate, were studied to determine the effect of the valine antimetabolite alpha-aminobutyric acid on growth and production of extracellular isoleucine and valine in an amino acid free medium. In the absence of alpha-aminobutyrate, these organisms actively excreted valine during growth (90-195 microgram/mL) but only accumulated limited concentrations of isoleucine (3-7 microgram/mL) in the culture broth. Growth of both organisms was reduced in the presence of 0.5-1.5% alpha-aminobutyrate but this inhibition was largely overcome by the use of preadapted inoculum. Metabolism of alpha-aminobutyrate was also increased using preadapted inoculum. During growth in the presence of 0.5-1.5% alpha-aminobutyrate, both organisms accumulated high concentrations of isoleucine (100-225 microgram/mL) while the normal accumulation of valine was unaffected. alpha-Ketobutyrate, a product of alpha-aminobutyrate metabolism, also stimulated isoleucine excretion by these organisms. The results are discussed in relation to the regulation of the biosynthetic pathways of isoleucine and valine in these rumen anaerobes and the potential significance of this amino acid excretion in ruminant nutrition.
mesh_terms: D000222:Adaptation, Physiological; D000613:Aminobutyrates / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism*; D005051:Eubacterium / Q000187:drug effects / Q000378:metabolism*; D007532:Isoleucine / Q000378:metabolism*; D012417:Rumen / Q000382:microbiology; D014633:Valine / Q000378:metabolism*
chemical_list: D000613:Aminobutyrates; D007532:Isoleucine; D014633:Valine