Salt Responses of Enzymes from Species Differing in Salt Tolerance

Enzymes which are affected by the addition of inorganic salts during in vitro assay were extracted from salt-sensitive Phaseolus vulgaris, salt-tolerant Atriplex spongiosa, and Salicornia australis and tested for sensitivity to NaCl. In each case malate dehydrogenase, aspartate transaminase, glucose 6-phosphate dehydrogenase, and isocitrate dehydrogenase showed NaCl responses similar to those found for commercially available crystalline enzymes from other organisms. Enzymes extracted from plants grown in saline cultures showed no important changes in specific activity or salt sensitivity. Interaction of pH optima and NaCl concentrations suggests that enzymes may differ in the way they respond to salt treatment.