Vanadium Catalysis in the Nonenzymatic Transamination of 8-Aminolevulinic Acid

By nonenzymatic model reactions, the influence o f vanadium (V 0 2+, V 0 3~) and other metal ions (A l3+, Fe2+, Fe3+, Zn2+, N i2+, Cr3+) on the transamination of 4,5-dioxovaleric acid (D O VA) with L-alanine (A la ) to 6 -aminolevulinic acid (<5-ALA) and pyruvic acid (P A ) with pyridoxal phosphate (P L P ) is investigated. The examinations o f the partial reactions show that V 0 2+, V 0 3~ and Fe2+ effectively enhance both conversions, while N i2+ only promotes the conversion of DOVA to 6 -ALA with pyridoxamine phosphate (P M P ). Besides Cr3+ , which inhibits the transaminations, all other metals tried slightly enhance both reactions. The coupled transamination DOVA/Ala to (5-ALA/PA with P L P as a catalyst is performed at 40 °C, the extent of the reaction being judged by the amount of 6 -ALA formed. Among all metal ions tested, V 0 2+ and V 0 3~ were found to be the most effective ones. Fe2+, A l3+ and Fe3+ also slightly enhance the reaction, but all other metals do not influence or inhibit the transamination. In presence of V 0 2+ or VO 3ions, the optimum pH of the reaction shifts from pH 4 to pH 7.4. The positive influence of vanadium on <5-ALA trans­ amination is discussed in connection with known structures of analogous Schiff base complexes with metal ions.