Vanadium Catalysis in the Nonenzymatic Transamination of δ-Aminolevulinic Acid

Abstract

Abstract By nonenzymatic model reactions, the influence of vanadium (VO2+, VO3−) and other metal ions (Al3+, Fe2+, Fe3+, Zn2+, Ni2+, Cr3+) on the transamination of 4,5-dioxovaleric acid (DOVA) with ʟ-alanine (Ala) to δ -aminolevulinic acid (δ-ALA) and pyruvic acid (PA) with pyridoxal phosphate (PLP) is investigated. The examinations of the partial reactions show that VO2+, VO3− and Fe2+ effectively enhance both conversions, while Ni2+ only promotes the conversion of DOVA to δ -ALA with pyridoxamine phosphate (PMP). Besides Cr3+ , which inhibits the transaminations, all other metals tried slightly enhance both reactions. The coupled transamination DOVA/Ala to δ-ALA/PA with PLP as a catalyst is performed at 40 °C , the extent of the reaction being judged by the amount of δ-ALA formed. Among all metal ions tested, VO2+ and VO3− were found to be the most effective ones. Fe2+, Al3+ and Fe3+ also slightly enhance the reaction, but all other metals do not influence or inhibit the transamination. In presence of VO2+ or VO3− ions, the optimum pH of the reaction shifts from pH 4 to pH 7.4. The positive influence of vanadium on δ-ALA transamination is discussed in connection with known structures of analogous Schiff base complexes with metal ions.