The Effect of Hydrogen Ion Concentration and of Inhibiting Substances on Urease

Nitrous oxide and ammonia emissions from N fertilization of maize crop under no-till in a Cerrado soil

“…Another possible explanation for the relatively low volatilization of NH 3 from urea, as well from ammonium sulfate, would be the low soil pH (Table 1). This factor can reduce up to 72% the velocity of urea hydrolysis by urease, as observed in the classical experiment of van Slyke and Zacharias (1914). However, it is known that even in acidic soil, significant NH 3 losses may occur because of the increasing of pH in the vicinity of the applied urea because of the consumption of H + following enzymatic hydrolysis of urea to NH 4 + (Overrein and Moe, 1967).…”

Renal Mechanisms Controlling Composition of the Body Fluids.

“…A precise micro method was needed for determination of urea, and Cullen and I decided to use the enzyme urease, which splits urea quantitatively into ammonia and carbon dioxide. To control accurately the action of this enzyme we undertook a study of its kinetics (40,48). This study led to evidence that the enzyme acts by combining in definite proportions with the urea, which after a definite mean time is thrown off as the hydrolytic products ammonia and carbon dioxide.…”

Determination of Ammoniacal and Urea Nitrogen

“…by Van Slyke and his co-workers (12,13), Fisher (3), and Kay and Sheehan (9). The latter have worked out a very careful technic for the determination of urea in blood.…”