The Effect of Univalent Cation Salts on the Stability and on Certain Physical Properties of Pyruvate Kinase

• Published in: The Journal of biological chemistry Vol. 242; no. 17; pp. 3825 - 3832
• Main Authors: Wilson, R H, Evans, H J, Becker, R R
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 10.09.1967
• Subjects: Ammonium Chloride; Chemical Phenomena; Chemistry; Chlorides; Lithium; Potassium Chloride; Pyruvate Kinase; Sodium Chloride; Spectrophotometry; Tromethamine; Tryptophan; Ultracentrifugation; Ultraviolet Rays
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)95823-0

The effects of a series of univalent cation salts on certain properties of pyruvate kinase, including sedimentation behavior, perturbation of tryptophan residues, and stability of the enzyme, have been investigated. Ultraviolet difference spectra of pyruvate kinase in 0.1 m solutions of activator univalent cation chlorides (K + , NH 4 + , or Na + ) in comparison with enzyme in 0.1 m nonactivator univalent cation chlorides (Li + , or trimethylammonium ion, or tris(hydroxymethyl)aminomethane cation) were determined. Tryptophanyl difference spectra with absorbance peaks at 286 mµ and 295 mµ were obtained under these conditions only when the nonactivator cation Tris + was included in the experiment. Difference spectra of pyruvate kinase in 0.1 m KCl versus enzyme in 0.1 m LiCl with or without various substrates and Mg ++ in the reaction showed no absorbance differences characteristic of the perturbation of tryptophan residues. In contrast, different comparisons of univalent cation chlorides at concentrations of 0.5 to 0.86 m showed capacities to perturb tryptophan residues of pyruvate kinase that were inversely correlated with the known capacities of univalent cations to activate the enzyme. A study of the stability of pyruvate kinase in a series of univalent cation salt solutions showed a positive correlation between the capacities of cations to protect against inactivation and known capacities to activate. In addition to the effect of univalent cations, different anion species influenced the extent of perturbation of tryptophan residues and the stability of the enzyme. The perturbation of the tryptophan residues in the presence of Tris + (cation) was inhibited by the addition of multivalent anions, phosphate, arsenate, and sulfate. Also, the enzyme consistently showed greater stability in buffer solutions containing the multivalent anions phosphate, arsenate, or sulfate than in buffer solutions in which the predominant anions were acetate, chloride, or nitrate. The sedimentation behavior of pyruvate kinase in the ultracentrifuge was not greatly affected by type of univalent cation salt in the environment, with the exception that the s 0 20, w value was lower in a solution of Tris-Cl than in other salts.