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J Bacteriol. 1968 January; 95(1): 37-42
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Salt Specificity of a Reduced Nicotinamide Adenine Dinucleotide Oxidase Prepared from a Halophilic Bacterium¹

^a Ames Research Center, NASA, Moffet Field, California 94035

ABSTRACT

Extracts prepared from a halophilic bacterium contained a reduced nicotinamide adenine dinucleotide (NADH₂) oxidase active at high solute concentrations. The cation requirement was nonspecific, since KCl, RbCl, and CsCl replaced NaCl with little or no loss of activity, and NH₄Cl was only partially effective. Only LiCl failed to replace NaCl. No specific chloride requirement was observed although not all anions replaced chloride. Bromide, nitrate, and iodide were essentially ineffective, whereas acetate, formate, citrate, and sulfate proved suitable. The presence of sulfate affected the ability of a cation to satisfy the solute requirement. Sulfate enhanced the rate of NADH₂ oxidation when compared with the rate observed in the presence of chloride. Cations which were inactive as chlorides (LiCl and MgCl₂ at high concentrations) satisfied the cation requirement when added as sulfate salts. Although magnesium satisfied the cation requirement, a concentration effect, as well as an anion effect, was observed. In the presence of MgCl₂, little NADH₂ oxidation was observed at concentrations greater than 1 M. At lower concentrations, the rate of oxidation increased, reaching a maximal value at 0.1 M and remaining constant up to a concentration of 0.05 M MgCl₂. Magnesium acetate and MgSO₄ also replaced NaCl, and the maximal rate of oxidation occurred at 0.05 M with respect to magnesium. There was no change in the rate of oxidation at high magnesium acetate concentrations, whereas the rate of NADH₂ oxidation increased at higher concentrations of MgSO₄.

¹ This paper was presented in part at the 67th Annual Meeting of the American Society for Microbiology, New York, N.Y., May 1967.