The Equilibrium between l-Aspartic Acid, Fumaric Acid and Ammonia in Presence of Resting Bacteria

Abstract

IT is an old observation that when fumaric acid, maleic acid or malic acid is heated in the presence of ammonia in a sealed tube to 2000 a conversion to aspartic acid occurs. There has been no evidence, however, that such a conversion can take place under biological conditions. Experiments which will be described in this paper show that l-aspartic acid is formed in a solution containing sodium fumarate, ammonium chloride and resting bacteria, no amino-acid being synthesised in the absence of the bacteria. The yield of l-aspartic acid, obtained under certain conditions, has been as high as 60 % of the fumaric acid taken. A small amount of aspartic acid is synthesised from malic acid but none, under our experimental conditions, from maleic acid. The results of experiments on oxidations, etc., in the animal body make it highly probable that the production of a-hydroxy-acids from a-amino-acids takes place via the a-ketonic acids. It will be shown in this paper, however, that aspartic acid in presence of resting bacteria rapidly liberates ammonia with the formation of fumaric acid. It is known that the latter slowly gives rise to malic acid (in presence of bacteria); hence it follows that aspartic acid presents an instance of an a-amino-acid proceeding to the corresponding hydroxy-acid via the unsaturated acid. Whether this is true in the animal body or with plant tissues still remains to be determined. Raistrick [1917] showed that in the case of organisms of the coli-typhosus group histidine produces the corresponding unsaturated acid, urocanic acid. With aspartic acid, it will be shown, a similar reaction occurs reversibly, the following equilibrium being established: 1-aspartic acid = fumaric acid + ammonia, and it is possible to obtain the equilibrium constant of this reaction. It is by no means a general phenomenon, however, that an a-amino-acid, in contact with B. coli, gives up ammonia to form the corresponding unsaturated acid. Under conditions such that aspartic acid readily loses ammonia to form fumaric acid, no liberation of ammonia has been observed to occur from 36-2

L ‐Aspartase: New Tricks from an Old Enzyme

“…Aspartase has no activity with either D-aspartic acid or crotonic acid (Virtanen and Ellfolk, 1955), and earlier work showed that glycine, alanine, glutamine, maleic acid, and glutaconic acid were not substrates (Quastel and Woolf, 1926). Also, L-cysteic acid, diaminosuccinic acid, leucine, mesaconic acid, aconitic acid, sorbic acid, and the diamine or mono-or diethyl esters of fumaric acid have all failed to show turnover with this highly specific enzyme (Virtanen and Tarnanen, 1932;Ellfolk, 1954).…”

The Role of the Krebs Cycle in Conjugation in Escherichia coli K-12

“…The demonstration in Escherichia coli of the reversible reaction aspartic acid+fumaric acid + ammonia (Quastel & Woolf, 1926), as well as the possession by this organism of a glutamic-aspartic transaminase (Lichstein & Cohen, 1944) rendered the first possibility feasible since these two systems, linked Parent cells (58-161 Hfr and W-1 F-) were washed with buffer (pH 7.2) and mated for 30 min. in buffer (pH 7*2)-glucose (20 pmole/ml.)-aspartate.…”

Enhancement of the Activity of -Aspartase from Escherichia coli W by Directed Evolution

“…The mutant enzymes with desired properties are screened for a defined goal [1]. This new strategy can be used to engineer any proteins or enzymes.L-Aspartase (L-aspartate ammonia-lyase, EC 4.3.1.1) catalyzes the reversible conversion of L-aspartate to fumarate and ammonia ion [2]. It is an important enzyme in industry.…”