Branched-chain Volatile Fatty Acids Research Articles

Effect of Leucine and Valine on Ketogenesis in the Ruminant1,2

Summary A study was made of the intermediary metabolism of l-leucine and dl-valine in the goat. The ketogenic nature of leucine was demonstrated both in the fasted and fed animal. Following intraruminal or intravenous infusion, leucine disappeared very rapidly from the blood and actually depressed the plasma level of amino acids in the fasted animal. Antiketogenic and glucogenic effects of valine were demonstrated following intraruminal or intravenous infusion. Effects similar to those of leucine and valine were exhibited by their metabolic intermediates, the branched-chain volatile fatty acids. The marked ketogenic effect of isovaleric acid was demonstrated following intraruminal infusion. There was a triphasic response in blood glucose similar to that occurring when other ketogenic fatty acids are placed in the rumen. Isobutyric acid exhibited marked glucogenic and antiketogenic properties when placed in the rumen.

Incorporation of isobutyrate and valerate into cellular plasmalogen by Bacteroides succinogenes.

Wegner, G. H. (University of Wisconsin, Madison) and E. M. Foster. Incorporation of isobutyrate and valerate into cellular plasmalogen by Bacteroides succinogenes. J. Bacteriol. 85:53-61. 1963.-Bacteroides succinogenes was found to require both a branched-chain volatile fatty acid (e.g., isobutyric) and a straight-chain acid (e.g., valeric) for growth. The organism used the acids as precursors for the synthesis of long-chain fatty acids and fatty aldehydes, which in turn were employed in the synthesis of phospholipid, mainly ethanolamine plasmalogen. Isobutyric acid was incorporated primarily into branched-chain C(14) and C(16) acids (tentatively identified as 12-methyl tridecanoic and 14-methyl pentadecanoic acids, respectively), and into fatty aldehydes. Valeric acid was used mainly for the synthesis of n-C(13) and n-C(15) fatty acids and fatty aldehydes. Apparently the two short-chain fatty acids were built up by the addition of two-carbon units to form the long-chain acids and aldehydes of the plasmalogen.

Metabolic function of branched-chain volatile fatty acids, growth factors for ruminococci. II. Biosynthesis of higher branched-chain fatty acids and aldehydes.

Allison, M. J. (Dairy Cattle Research Branch, USDA, Beltsville, Md.), M. P. Bryant, I. Katz, and M. Keeney. Metabolic function of branched-chain volatile fatty acids, growth factors for ruminococci. II. Biosynthesis of higher branched-chain fatty acids and aldehydes. J. Bacteriol. 83:1084-1093. 1962.-A number of strains of rumen bacteria require branched-chain volatile fatty acids for growth. A strain of Ruminococcus flavefaciens that requires either isovalerate or isobutyrate incorporates radioactive carbon from isovalerate-1-C(14) and isovalerate-3-C(14) into leucine and into the lipid fraction of the cells. Evidence obtained by both paper and gas chromatography indicated that most of the label in the lipid of cells grown in isovalerate-1-C(14) was in a branched-chain 15-carbon fatty acid, with some in a 17-carbon acid; about 7.5% of the C(14) was recovered in a branched-chain 15-carbon aldehyde. The aldehydes were in the phospholipid fraction and were presumably present as plasmalogen.A strain of R. albus was shown to require isobutyrate, 2-methyl-n-butyrate, or 2-ketoisovalerate for growth. This strain did not incorporate appreciable C(14) from isovalerate-1-C(14) or isovalerate-3-C(14). When grown in a medium containing isobutyrate-1-C(14), most of the cellular C(14) was found in the lipid fraction. Analysis of the lipid demonstrated that the label was present mainly as branched-chain 14-carbon and 16-carbon fatty acids, with 11% of the C(14) present in 14- and 16-carbon carbonyl compounds, presumably branched-chain aldehydes.Branched-chain 14-, 15-, and 16-carbon fatty acids are major components of the lipids of these rumen bacteria. The possibility that these acids and aldehydes, which are found in ruminant body and milk lipids, may be of microbial origin is discussed.

Studies on the metabolic function of branched-chain volatile fatty acids, growth factors for ruminococci. I. Incorporation of isovalerate into leucine.

Allison, Milton J. (Dairy Cattle Research Branch, U. S. Department of Agriculture, Beltsville, Md.), M. P. Bryant, and R. N. Doetsch. Studies on the metabolic function of branched-chain volatile fatty acids, growth factors for ruminococci. I. Incorporation of isovalerate into leucine. J. Bacteriol. 83:523-532. 1962.-Ruminococcus flavefaciens strain C94, a cellulolytic rumen bacterium, requires either isobutyrate or isovalerate for growth. The organism was grown in the presence of C(14)-labeled isovalerate, and the metabolic fate of the labeled carbon was studied to obtain information on the functions of this growth factor. Radioactivity from isovalerate-1-C(14) and isovalerate-3-C(14) was found mainly in the protein and lipid fractions of the cells. The C(14) in protein was all in leucine, indicating that a function of isovalerate was to serve as a carbon skeleton for leucine synthesis. As C(14) in leucine synthesized from isovalerate-1-C(14) was entirely in carbon 2, the intact isovalerate molecule was apparently incorporated into leucine. This is evidence that leucine was synthesized by a mechanism different from that previously demonstrated in other microorganisms.R. flavefaciens has a definite but limited ability to incorporate exogenous amino acids, including leucine. It incorporated 2% of the C(14) during growth in uniformly labeled (UL) C(14)-Chlorella protein hydrolyzate; Escherichia coli incorporated 37% of the label under similar conditions. In another experiment, a limited amount of exogenous leucine-2-C(14) was incorporated into protein of R. flavefaciens. The requirement for isovalerate was not replaced by dl-leucine or 2-ketoisocaproate. It is suggested that isovalerate or isobutyrate is required because R. flavefaciens has a limited ability to incorporate exogenous branched-chain amino acids and a limited ability to synthesize the isopropyl group found in these amino acids and in other components of the cell.