Glutamate dehydrogenase kinetics

Kurz and Frieden in 1977 and 1980 determined -secondary kinetic isotope effects for the unusual desulfonation reaction shown in Table 1, both in free solution and with enzyme catalysis by glutamate dehydrogenase. The isotope effects (H/D) were in the range of 1.14-1.20. At the time, the correct equilibrium isotope effect had not been reported and their measurements yielded an erroneous value... 

E2. Ellis, G., and Goldberg, D. M., Optimal conditions for the kinetic assay of serum glutamate dehydrogenase activity at 37°C. Clin. Chem. 18, 523-527 (1972). 

Rife JE, Qeland WW. Kinetic mechanism of glutamate dehydrogenase. Biochemistry 1980 19 2321-2328. 

Sampson EJ, Baird MA. Chemical inhibition used in a kinetic urease/glutamate dehydrogenase method for urea in serum. Clin Chem 1979 25 1721-9. 

Experience with model calculations for equilibrium isotope effects and kinetic isotope effects, when using conventional TST, shows that the RGM is valid in the common circumstance in which the effects of coupled vibrational motions cancel between reactant and product states, or between reactant and transition states. The natural coupling expected between the various bends and stretches of the bonds in a methyl group is largely the same in the reactant state and transition state in the acetyl transfer example, so the free-energy effects of multiple isotopic substitutions are strictly additive. In the case of the glutamate dehydrogenase reaction of Fig. 

The amino acid specificity of glutamate dehydrogenase is known to be broad (e.g.. References 26,27). Since the reaction is reversible, the a-keto acid specificity should also be correspondingly broad. Indeed, Table I shows that glutamate dehydrogenase can catalyze the reductive amination of at least 10 a-keto acids. It should be noted that kinetic data were determined in die presence of a low ammonia concentration (5mM) in order to obtain realistic parameters for the design of optimal... 

Soluble copolymers of albumin and L-glutamate dehydrogenase have been prepared by glutaraldehyde cross-linking. The kinetic and electron microscopic properties of the soluble derivatives were compared with data available concerning the enzyme immobilized within proteic films. 

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