THE ISOLATION AND CRYSTALLIZATION OF THE ENZYME UREASE PRELIMINARY PAPER

After work both by myself and in collaboration with Dr. V. A. Graham and Dr. C. V. Noback that extends over a period of a little less than 9 years, I discovered on the 29th of April a means of obtaining from the jack bean a new protein which crystallizes beautifully and whose solutions possess to an extraordinary degree the ability to decompose urea into ammonium carbonate. The protein crystals, which are shown in Fig. 1, have been examined through the kindness of Dr. A. C. Gill, who reports them to be sharply crystallized, colorless octahedra, belonging by this definition to the isometric system. They show no double refraction and are from 4 to 5,~ in diameter. While the most active solutions of urease prepared in this laboratory by Sumner, Graham, and Nobackl and by Sumner and Graham2 possessed an activity of about 30,000 units per gm. of protein present, the octahedra, after washing away the mother liquor, have an activity of 100,000 units per gm. of dry material. In other words, 1 gm. of the material will produce 100,000 mg. of ammonia nitrogen from a urea-phosphate solution in 5 minutes at 20°C. At this temperature the material requires 1.4 seconds to decompose its own weight of urea. The crystals, when freshly formed, dissolve fairly rapidly in distilled water, giving a water-clear solution after centrifuging from the slight amount of insoluble matter that is present. The solution coagulates upon heating and gives strongly the biuret,