Multimethod characterization of the interaction of aluminum ion with α-ketoglutaric acid in acidic aqueous solutions

It has recently been reported that aluminum plays a very important role in reducing the activity of Krebs-cycle enzymes and glutamate dehydrogenase in rat brain homogenate. Therefore, it is necessary to identify the aluminum binding ability with the pivotal substrate alpha-ketoglutarate in biological systems. The interactions of aluminum with alpha-ketoglutarate were studied with pH-potentiometry, cyclic voltammetry, UV-vis, H-1, Al-27-NMR and Raman spectra multi-analytical techniques in acidic aqueous solution to measure the stoichiometries and stability constants of the complexes and its ketoenol tautomerism. The alpha-ketoglutarate was found to bind Al in a bidentate manner at the carboxylate and carbonyl moieties. The mononuclear 1:1 (AILH(-1), AIL(+), AIHL(2+)) and 2:1 (AIL(2)(-), AlL2H-2 (3-)) species, and dinuclear 2:1 (Al2L4+) species were found in acidic aqueous solution. Meanwhile, Al can promote aalphaKG tautomerize to its enolic-structure compounds in solutions. These findings may help to further understand the influence of Al on GDH enzyme reactions in biological systems.