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

The majority of recent temperature studies which have been made on enzyme systems indicate that their rate, like that of chemical reactions, increases exponentially with the absolute temperature in accordance with the Arrhenius equation. With enzymes, however, this temperature activation ceases above the inactivation temperature of the enzyme. For a specific enzyme system the energy of activation (,M in the Arrhenius equation) is constant over a considerable range of temperature; this constancy of /L is characteristic of such systems as the fat oxidation system of Lupinus albus (Craig, 1936), yeast and malt invertases (Sizer, 1937), dehydrogenases of Escherichia coli (Gould and Sizer, 1938), human and cat bone phosphatase (Bodansky, 1939), jack bean and soy bean urease (Sizer, 1939, 1940), heart dehydrogenase and oxidase (Hadidian and Hoagland, 1939), and purine and aldehyde oxidase of milk (Sizer and Gould, 1940). Constant activation energies characterize intracellular as well as extracellular enzyme systems, and no change in activation energy accompanies the extraction of an enzyme from the cell (Sizer, 1938, 1940). Information concerning the biochemical relationships of enzymes can be obtained by comparing the activation energies of enzymes from different species. In this respect the invertase