Abstract
Since Takeuchi 1 discovered a “selective enzyme,” urease, in soy bean (the seeds of Glycine hispida), more than fifteen methods have been developed for the preparation of urease solution or powder for the determination of urea in blood and in urine. Experience has shown that each has its own advantage and all have the same disadvantage. 2
No attempt has been made to try all of these methods. However, it is worth while to determine which one gives the best results and which is, therefore, best adapted to routine work. At random, the methods proposed by Armstrong and Horton and by Folin and Wu were selected for trial and used to compare the extractions from Jack bean meal with 10, 5, and 2 per cent sodium chloride solution, and with distilled water (5 gm. meal in 100 cc. solvent). Since Sumner and his co-workers 3 believe that urease is a protein and since the vegetable proteins can be extracted by sodium chloride solutions of different strengths and by water, it is thought that extraction from Jack bean meal with sodium chloride solution of a certain strength may be of a high activity.
In all the experiments urease extracted with 5 or 2 per cent sodium chloride solution or with distilled water, and the one prepared according to the directions of Arrnstrong and Horton seems to be more active in decomposing urea than the alcoholic extract prepared according to the method of Folin and Wu. The former recovers 99 per cent of urea while the latter recovers only 92 per cent. The one prepared with 10 per cent sodium chloride solution gives nearly the same result as the Folin and Wu urease solution, which may be explained by the depressing effect of sodium ion. 4
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