Four isoforms of glutamine synthetase in light-grown soybeans.

Glutamine synthetase (GS) activity recovered from linear sucrose gradients was associated with the cytosol of cells isolated from etiolated soybean hypocotyls whereas light-grown tissue contained increased GS activity localized in both the cytosol and chloroplasts. DEAE-cellulose chromatography indicated two GS isoforms in etiolated hypocotyls whereas light-grown hypocotyls and primary leaves contained four isoforms. Only one GS isoform was recovered from both etiolated and light-grown cotyledons.