Stimulation of bicarbonate incorporation by ammonium in nonphotosynthetic cell suspension cultures of Acer pseudoplatanus

Abstract

Ammonium supplied to Acer cells incubated in Tricine buffer raised net dark incorporation of 14C‐bicarbonate by 1.5 to 3.3 fold; this stimulation was not abolished by prior inhibition of glutamine synthetase by methionine sulphoximine. With cells in phosphate buffer, ammonium gave a smaller 1.15 to 1.3 fold stimulation which was abolished when glutamine synthetase was inhibited. Ammonium had no direct effect on the activities of phosphoenolpyruvate carboxylase and pyruvate kinase assayed in partially purified extracts or on the enzymes catalysing release of label.