Effect of lithium salts on lactate dehydrogenase, adenylate kinase, and 1-phosphofructokinase activities

Figures & data

Figure 1.  Effect of lithium salts on 30 nM RMAK. The 30 nM RMAK was diluted from a 3 µM RMAK stock in 0.01 M potassium phosphate, pH 8 buffer. The activity of RMAK was control, 0.016 eu/mL. The diluted preparations were incubated for 1 h at 25°C and the activities were then determined (see “Methods”).

Figure 2.  Effect of lithium anions on 30 nM RPFK-1 activity. A 30 nM RPFK-1 was prepared as given in the “Methods” section containing the quantities of lithium salts shown. The preparations were incubated for 1 h at 25°C and the activities were then determined. The RPFK-1 activity of the control was 0.018 ± 0.022 eu/mL.

Figure 3.  Effect of substrates on 30 nM RPFK-1 inhibition by Li₂CO₃. A 30 nM RPFK-1 control (▪) with no additions was prepared as given in the “Methods” section containing the quantities of lithium salts shown. The final additions to the control shown are 100 mM F 6-P (•), and 100 mM ATP-Mg (○). In the absence of Li₂CO₃ average activities were as follows: control, 0.020 eu/mL; plus F 6-P, 0.018 eu/mL; and plus ATP-Mg, 0.015 eu/mL.

Figure 4.  Effect of 5 µM aldolase on PFK-1 inhibition by Li₂CO₃. A 30 nM RPFK-1 was prepared as given in the “Methods” section containing the quantities of lithium salts shown. The preparations were incubated for 1 h at 25°C and the activities were then determined. The RPFK-1 activity of the control was 0.020 ± 0.002 eu/mL.

Figure 5.  Effect of RPFK-1 concentration on inhibition by 0.075 M Li₂CO₃. Concentrations of RPFK-1 were prepared by dilutions of a 3 µmol stock as given in the “Methods” containing 0.075 M LiCO₃ or not (controls) as shown. Preparations were incubated for 1 h at 25°C and the activities were then determined. The RPFK-1 activity of the control was 0.020 ± 0.002 eu/mL. The RPRK-1 activities of stock controls were as follows: 30 nmol, 0.017 eu/mL; 100 nmol, 0.044 eu/mL; and 200 nmol, 0.29 eu/mL.

Figure 6.  Effect of potassium and sodium salts on 30 nM RPFK-1 activity. The figure is a composite of several experiments using the average of 0.017 eu/mL as the control value for relative activities of 1.00. The 30 nM RPFK-1 solutions were made as given in the “Methods” section, incubated for 1 h; solutions were then made to salt concentrations shown, with an additional 1 h incubation, when RPFK-1 activities were determined. All solutions were maintained at pH 8. The symbols for the salts are as follows: KCl, □; K₂CO₃, ○; K₂HPO₄, Δ; NaCl, ▪; Na₂CO₃, •; and Na₂HPO₄, ▴.

Figure 7.  Effect of acetate salts on 30 nM RPFK-1 activity. The figure is a composite of several experiments using the average of 0.010 eu/mL as the control value for relative activities of 1.00. The 30 nM RPFK-1 solutions were made as given in the “Methods” section, incubated for 1 h; solutions were then made to salt concentrations shown, with an additional 1 h incubation, when RPFK-1 activities were determined. All solutions were maintained at pH 8. The symbols for the salts are as follows: sodium acetate, ▪; lithium acetate, •; and potassium acetate, ○.

Table 1.  Percent inhibition of 30 nM RPFK-1 by 0.1 M monovalent salt.

Cation	Anion
	Carbonate	Chloride	Acetate	Sulfate	Phosphate
Lithium	80	–5	–20	48	—
Potassium	35	60	0	75	65
Sodium	40	20	25	25	20

Note. Data for this table derive from Figures 2 and 4–6 and a previous study¹. —, lithium phosphate was too insoluble for these studies.

Russell P, Williams A, Marquez K, Hua T, Ehya F, Hardamon C, et al. Effect of ammonium, sodium, and potassium ions on rabbit muscle phosphofructokinase-1 and adenylate kinase activities, J Enzyme Inhib Med Chem 2009;24;1–7.

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