Ligand-induced changes in the conformational stability and flexibility of glutamate dehydrogenase and their role in catalysis and regulation.

Bovine glutamate dehydrogenase (GDH) is allosterically regulated and requires substrate-induced subunit interactions for maximum catalytic activity. Steady-state and presteady-state kinetics indicate that the rate-limiting step depends on the nature of the substrate and are likely associated with conformational fluctuations necessary for optimal hydride transfer. Deuterated glutamate shows a steady-state isotope effect but no effect on the presteady-state burst rate, demonstrating that conformational effects are rate limiting for hydride transfer while product release is overall rate limiting for glutamate.