Kinetic Mechanism in the Absence of Metal of Hafnia alvei Aspartase in the Amination Direction

The kinetic mechanism of Hafnia alvei aspartase in the amination direction has been determined in the absence of metal. The initial velocity pattern obtained by varying the concentration of fumarate at several fixed concentrations of NH4+ , shows an intersection on the left of the ordinate at pH 7.0, indicating that the kinetic mechanism is a sequential mechanism in which substrate inhibition by fumarate is observed. The dead-end inhibition pattern by varying the concentration of NH4+ at several fixed concentration of succinate shows an intersection on the left of the ordinate. These data are consistent with random addition of NH4+, or fumarate. The Haldane relationship gives a Keq of 1.18 10-3 M at pH 7.0, which is in agreement with the values obtained from the direct determination of reaction concentrations at equilibrium (6.0 10-3 M).