Adenylate Concentrations in Chara: Variability, Effects of Inhibitors and Relationship to Protoplasmic Streaming

Abstract

The concentrations of ATP, ADP and AMP In Chara vary considerably depending on the culture conditions. The ranges of cytoplasmic concentrations were: ATP, 1 6-3 4 mM; ADP, 0 1-1 1 mM; AMP <O 6 mM. The ATP concentration was lower in the dark than in the light by 5-25%. The cytoplasmic concentration of inorganic phosphate in cells from one culture was 21 2 mM. From these values AGATp lies in the range 47-52 kJ mol-I. Lowering of the ATP concentration by metabolic inhibitors CCCP (carbonyl cyanide mchlorophenylhydrazone), DCCD (N,N'-dicyclohexylcarbodiimide) and DCMU (3-(3-chloropheny1)-1, I-dimethylurea) was associated with almost parallel changes in the rate of protoplasmic streaming. The use of streaming rate as an in vivo indicator of ATP status is discussed. The results are consistent with the participation of adenylate kinase in the regulation of adenylate concentrations.