Relative Deamination Rates of Amino Acids by Rumen Microorganisms

Abstract

Summary Studies were made of the relative deamination rates of amino acids in vitro by rumen microorganisms. Two media were investigated—cheesecloth-strained rumen liquor and washed suspensions of rumen bacteria. Individual amino acids may be divided into three groups with regard to their relative rate of deamination. Serine, cysteine, aspartic acid, threonine and arginine were attacked most completely, followed by glutamic acid, phenylalanine, lysine, and cystine forming an intermediate group and a third group in which deamination was much less pronounced was tryptophane, δ-amino valeric acid, methionine, alanine, valine, isoleucine, ornithine, histidine, glycine, proline, and hydroxyproline. Dissimilation rates are more rapid and complete in rumen liquor than in washed cell suspensions. A mixture of three or four amino acids were not dissimilated to a greater degree than the catabolic summation of each individual amino acid in the mixture. The D and L forms of serine and tryptophan were catabolized at the same relative rate whereas the D enantiomorphs of aspartic acid, lysine, threonine, and phenylalanine were not catabolized. Modifications of the washed cell medium failed to demonstrate the factors responsible for the marked decrease in deaminating power.