Assay of partially purified glutamate dehydrogenase isolated from asparagus beans for VMAX and KM as a measure of its role in ammonium ion assimilation

Abstract

Glutamate dehydrogenase (E C 1.4.1.1) isolated from the seeds of asparagus beans was partially purified to a factor of 22 by dialysis after fractional precipitation with solid ammonium sulphate at 40 and 60% saturation. A specific activity of 11.78μmol min^-1 mg^-1 protein was calculated for the partially purified enzyme when the NAD⁺ - linked deaminating activity was assayed with glutamate as the substrate (ranging in concentration from 8.33 mM to 33.33 mM). From the Lineweaver – Burk plot, the V_max and K_m, representing the maximum velocity and Michaelis constant, respectively were deduced. Vmax was found to be 25 μmol min^-1 while the Km was 33 mM.

Keywords: Glutamate dehydrogenase, asparagus beans, enzyme, ammonium ion

International Journal of Natural and Applied Sciences Vol. 2 (3) 2006: pp. 197-200