The Digestion and Inactivation of Crystalline Urease by Pepsin and by Papain

The identity of the enzyme urease with the octahedral globulin crystals isolated by the senior author from the jack bean in 1926 (1) has been challenged by Waldschmidt-Leitz and Steigerwaldt (2). These investigators published a paper in which they claimed that crystalline urease is not inactivated at pH 7.0 by incubation with trypsin or papain, while the protein component of the urease undergoes digestion to such an extent that after 48 hours at 30’ no more than a hardly perceptible precipitate is given upon adding sulfosalicylic acid. We have shown (3) that the experimental work of WaldschmidtLeitz and Steigerwaldt is not to be accepted since their digests contained only 1 part of crystalline urease in 67,000, at which dilution urease gives a hardly perceptible precipitate with sulfosalicylic acid, and since the precipitate which is given by proteins present in the trypsin itself is so heavy as to interfere and to prevent one from drawing any conclusion concerning the amount of precipitate given by the urease. We have carried out digestions in which the urease precipitable with sulfosalicylic acid has been determined gravimetrically both before and after incubation with trypsin and have shown that no significant amount of digestion could have occurred. Finally, by making use of the delicate reaction between urease and antiurease, we have demonstrated that during incubation with trypsin the decrease of the protein component of urease proceeds at the same rate as diminution of urease activity. In reply to our paper Waldschmidt-Leitz and Steigerwaldt (4)