COORDINATION CHEMISTRY OF MICROBIAL IRON TRANSPORT COMPOUNDS .16. ISOLATION, CHARACTERIZATION, AND FORMATION-CONSTANTS OF FERRIC AEROBACTIN

Aerobactin, a dihydroxamate derivative of citric acid, is a siderophore produced by Aerobacter aerogenes. The iron complex has been isolated from neutral aqueous solutions as the trisodium salt. The high-spin octahedral complex is formed using the two bidentate hydroxamate groups and the central carboxylate and hydroxyl moieties of the citrate backbone. Ferric aerobactin exists predominantly as the A optical isomer in aqueous solution. The stability constants (logβ113 = 31.74, log β112 = 29.70, log (β111 = 26.68, log β110 = 23.06, logβ111 = 18.48) and redox potential have also been determined from spectroscopic, potentiometric titration, and electrochemical techniques. The implication of these results to the mechanisms of iron uptake and release by A. aerogenes is discussed. © 1979, American Chemical Society. All rights reserved.