Metabolism of Arginine, Citrulline, Ornithine and Proline by Starved Rumen Ciliate Protozoa

Abstract

Studies were initiated to examine the formation of urea and/or ammonia from arginine and some other amino acids, and the metabolism of arginine, citrulline, ornithine, and proline in a starved rumen ciliate protozoal suspension. Not urea but ammonia was produced from arginine and also from citrulline, ornithine, aspargine and glutamine of the 10 amino acids tested. Urea was not hydrolysed. Using labeled compounds, citrulline was paper- and column-chromatographically identified as the first intermediate in arginine metabolism. Citrulline, ornithine and proline were converted to ornithine, proline and δ-aminovalerate (DAV), respectively. DAV underwent no more degradation. The ability to reduce proline to DAV decreased with the incubation time for preparing the starved ciliate suspension. Appreciable amounts of arginine and arginine with citrulline were synthesized from citrulline and ornithine, respectively.