Temperature Activation of the Urease-Urea System Using Urease of Proteus vulgaris

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Abstract
At all temps. rate of urea hydrolysis catalyzed by the intracellular urease of P. vulgaris does not vary with time. In the temp. range from 0.2 to 50[degree] the rate increases exponentially with temp. in accordance with the Arrhenius equation where the energy of activation is 14,400, or 11,700, or 8,700 cal. per gram mole, depending upon the metabolism of the organism, the age of the culture and the composition of the urea digest. With certain bacterial prepns. the activation energy is 14,400 or 11,700 cal. below and 8,700 cal. above a critical temp. When the bacteria were grown in a medium lacking urea, activation energies of only 11,700 or 8,700 cal. characterized the urease-urea system; the presence of urea in the growth medium favored the occurrence of the 14,400 value. The urease conc. per bacterial cell is differentially stimulated by the addition to the growth medium of urea, amino acids, or nicotinic acid. The fact that the activation energies of 11,700 and 8,700 cal. for the P. vulgaris system are identical with those of the urease system of jack and soy beans suggests a close similarity in the ureases of these widely different species.

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