Metabolic regulation of glutamate dehydrogenase
Glutamate dehydrogenase (GDH), a key control enzyme interrelating carbohydrate and amino acid metabolism, was investigated with respect to coenzyme utilization and regulatory control via allosteric effectors. GDH from gall fly larva, Eurosta solidaginis, was purified and kinetic studies suggested that it was preferentially NADP-linked. Temperature effects on the regulatory properties of this GDH, including ATP/GTP interactions, may be responsible for the increase in proline seen at low temperature in the overwintering larva. GDH from the intertidal sea anemone, Anthopleura xanthogrammica, was purified and found to be NADP(H)-specific. This GDH was not regulated by nucleotide effectors but was strongly affected by ions. The dual coenzyme specific GDH from bovine liver was investigated with respect to its coenzyme preference. The data suggested that under increasing glutamate concentrations the preferred coenzyme was NADP, a preference which was promoted by the action of metabolic modulators.