The Preparation of Citrulline by Hydrolysis of Arginine

The need for 50 gm. of citrulline for the thermal data being compiled in this laboratory (1, 2) led to the search for a suitable method of preparation of this compound. Of the methods available, the most practical were Kurtz’s ingenious three reaction degradation of arginine (3), and Wada’s tryptic digestion of casein (4). Each of these authors, however, reported the preparation of less than 2 gm. of citrulline, and neither method is of the type to lend itself readily to the processing of larger batches. The necessity for troublesome barium hydroxide and sealed tube manipulations in one case, and a 3 week incubation in the other, increased the desirability of a rapid and simple process. Although the biological conversion of arginine to citrulline is well known (5, 6), these reactions are inconvenient as preparative procedures. The alkaline hydrolysis of arginine has been shown to give ornithine (7, 8), urea (9), and carbon dioxide and ammonia (10). The suggestion that citrulline might similarly be obtained has been offered, and at least one such attempt has been recorded (3, 5, 11). The hydrolysis of arginine may be represented as follows :