Abstract
In view of their possible involvement in ammonium assimilation in the coral/algal symbiosis, we have purified two distinct glutamate dehydrogenase isoenzymes from the symbiotic dinoflagellate Symbiodinium microadriaticum (Freudenthal) extracted from the staghorn coral Acropora formosa collected from Magnetic Island, North Queensland, Australia, in 1986–1987. An NADPH-specific glutamate dehydrogenase (GDH) displayed biphasic kinetics with respect to ammonium as the variable substrate; at low substrate concentrations the apparent K m was below 1 mM, whereas at high substrate concentrations the corresponding value was approximately 200 mM. The NADPH-GDH displayed extremely low activity in the direction of glutamate oxidation; together with the kinetic data this suggests a probable role in ammonium assimilation. A second (NADH-specific) GDH was found to have both amination and deamination activities, and presumably functions in vivo in glutamate oxidation. Kinetic constants are reported for both GDH isoenzymes.
Similar content being viewed by others
Literature cited
Bradford, M. M. (1976). A rapid and sensitive method for the quantitation of microgram quantities of protein using the principle of protein-dye binding. Analyt. Biochem. 72: 248–254
Catmull, J., Yellowlees, D., Miller D. J. (1987). NADP+-dependent glutamate dehydrogenase from Acropora formosa: purification and properties. Mar. Biol. 95: 559–563
Dudler, N., Yellowlees, D., Miller, D. J. (1987). Localization of two L-glutamate dehydrogenases in the coral Acropora latistella. Archs Biochem. Biophys. 254: 368–371
Gayler, K. R., Morgan, W. R. (1976). An NADP-dependent glutamate dehydrogenase in chloroplasts from the marine green alga Caulerpa simpliciuscula. Pl. Physiol. 58: 283–287
Gunnersen, J., Catmull, J., Yellowlees, D., Miller, D. J. (In preparation). Ammonium uptake and assimilation in Symbiodinium microadriaticum.
Koshland, D. E., Jr., Nemethy, G., Filmer, D. (1966). Comparison of experimental binding data and theoretical models in proteins containing subunits. Biochemistry, N. Y. 5: 365–385
Laemmli, U. K. (1970). Cleavage of structural proteins during the assembly of the head bacteriophage T4. Nature, Lond. 227: 680–685
Neet, K. E. (1980). Cooperativity in enzyme functions: equilibrium and kinetic aspects. Meth. Enzym. 64: 139–193
Oshawa, K., Ebata, N. (1983). Silver stain for detecting 10-femtogram quantities of protein after polyacrylamide gel electrophoresis. Analyt. Biochem. 135: 409–415
Streamer, M., McNeil, Y., Yellowlees, D. (1986). The short-term partitioning of carbon-14 assimilate between zooxanthellae and polyp tissue in Acropora formosa. Mar. Biol. 90: 565–573
Trench, R. K. (1986). Dinoflagellates in non-parasitic symbioses. In: Taylor, F. J. R. (ed.) Biology of the dinoflagellates. Blackwell Scientific Publications, London, p. 530–570
Author information
Authors and Affiliations
Additional information
Communicated by G. F. Humphrey, Sydney
Rights and permissions
About this article
Cite this article
Dudler, N., Miller, D.J. Characterization of two glutamate dehydrogenases from the symbiotic microalga Symbiodinium microadriaticum isolated from the coral Acropora formosa . Mar. Biol. 97, 427–430 (1988). https://doi.org/10.1007/BF00397773
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00397773