Kinetic Study of Enzymatic Urea Hydrolysis in the pH Range 4–9

M. Fidaleo and R. Lavecchia

Abstract
The enzymatic hydrolysis of urea by jack bean urease was investigated at 25 °C over the pH range 4–9. Reaction rate data were found to be well described by a modified Michaelis-Menten equation with a pH-dependent rate coefficient and a product inhibition term. The influence of pH on activity was interpreted in terms of perturbation of the enzyme distribution among three differently protonated forms. Kinetic analysis yielded a Michaelis constant of 3.21 mmol l–1 and indicated that the inhibition mechanism was of the fully non-competitive type, with KP = 12.2 mmol l–1. The estimated activation energy was 35.3 kJ mol–1. The resulting kinetic expression was tested by comparing model predictions with the experimental behaviour observed in unbuffered media and over a long-term period.

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Keywords
enzyme kinetics, urease, urea, hydrolysis