Abstract: The conversion of ammonia and fumaric acid to aspartic acid is demonstrated in vitro withenzyme suspensions prepared from etiolated soybean and mung bean sprouts as well as from leaves of spinach and alfalfa, and from wheat seedlings The plant tissues were ground in Waling blendor, in presence of phosphate buffer pH 7.2. The pulp, after freeing from fibrous material, was twice precipitated with acetic acid at pH 4.6, centrifuged, and resuspended in phosphate buffer pH 7.2. To 8 ml of the above enzyme suspension were added 1 ml of 0.2 N sodium fumarate and 1 ml 0.2 N ammonium sulphate as reactants. The mixture was left to react, with the addition of a few drops of toluene to prevent bacterial growth, at 25℃ for 9,4 hours. At the end of the incubation period, the contents were chromatographed on filter paper with water-saturated phenol as solvent. A distinct spot of aspartic acid appeared after treatment with ninhydrin solution. It was taken to be the evidence of enzymic synthesis of aspartic acid since neither the enzyme suspension nor the reactants mixture incubated alone under the same condition produce any detectable amount of aspartic acid. That the aspartic acid formed is through direct addition of ammonia on to fumarate is demonstrated in the case of soybean by the inability of either succinate or malate to replace fumarate in this reaction.