Studies on the Aspartic Acid Decarboxylase of Rhizobium Trifolii.

Virtanen and Laine (1937) were the first to suggest the existence of an aspartic acid decarboxylase in Rhizobium trifolii, by the isolation of beta-alanine from a 47-day fermentation mash containing aspartic acid. Shive and Macow (1946), working with hydroxyaspartic acid as a competitive analogue for aspartic acid in the metabolism of Escherichia coli, found that the addition of this compound to the growth medium inhibited the proliferation of the organism and that this inhibition was completely prevented by the addition of aspar(ic acid, pantothenic acid, or beta-alanine. They concluded from these results that aspartic acid was the precursor of beta-alanine, which in turn becomes part of the pantothenic acid molecule. It has been reported recently (Mardeshev et al., 1948, 1949) by several Russian workers that they have found an organism, Pseudomycobacterium, that is capable of decarboxylating aspartic acid, as measured by C02 production in a Warburg vessel. They further state that the enzyme has been prepared in a cell-free state (Mardeshev et al., 1948) and that the coenzyme of the decarboxylase has been found to be pyridoxine phosphate (Mardeshev et al., 1949). It has more recently been reported from this laboratory (Billen and Lichstein, 1949) that washed cell suspensions of Rhizobium trifolii contain an aspartic acid decarboxylase as determined by microbiological analysis for the end product of the decarboxylation, beta-alanine. Because of the importance of such an enzyme, further studies have been made and the data are herewith presented.