A new high-performance liquid chromatography assay for glutamine synthetase and glutamate synthase in plant tissues

Abstract Glutamic acid and glutamine, formed in plant tissue extracts by glutamate synthase and glutamine synthetase, respectively, were separated by derivatization with o -phthaldialdehyde followed by reverse-phase high-performance liquid chromatography on a μBondapak C 18 column. The derivatives were eluted by isocratic elution, and the mobile phase was a 20 m m sodium phosphate buffer (pH 6.8) with 36% methanol. The procedure is rapid, sensitive, and requires a minimum sample.