STUDIES ON THE ASPARTIC ACID DECARBOXYLASE OF RHIZOBIUM TRIFOLII

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Abstract
A modified medium for the microbiological assay of beta-alanine is descr. R. trifolii was found to contain an enzyme system capable of decarboxylating aspartic acid to beta-alanine, as detd. by microbiological assay for this compound. A study of the properties of the system was undertaken with the following results: (1) The age of the culture markedly affected enzyme activity; the greatest activity occurring during the logarithmic phase of growth. (2) No marked effect of growth temp. between 22 and 38 [degree]C was noted on enzyme activity. (3) The opt. temp, of activity of washed cells appeared to be 46[degree]C. The calculated slope of beta-alanine production vs. time was greatest at this temp. (4) The enzyme shows a pH opt. between pH 5.2 and 6.2 in phosphate buffer, with the activity falling off sharply on either side of this range. (5) The production of beta-alanine is markedly influenced by substrate concn. The enzyme was found to be present in Escherichia coli (Texas) and R. trifolii, but absent under the conditions of the expts. in Lactobacillus bulgaricus, Streptococcus lactis R, Corynebacterium diphtheriae, Saccharomyces fragilis, Micrococcus pyogenes var. albus, and Aerobacter aerogenes.