Effect of Illumination and Bivalent Metal Ions on Oxidation Reactions of PQQ.
Lousine Boyadzhyan
Faculty Advisor: Tetsuo Otsuki

     Heterocyclic redox cofactor PQQ (pyrroloquinoline quinone) is found in the prosthetic group of such dehydrogenases as methanol and glucose. Here we study PQQ found in a homodimeric enzyme, soluble glucose dehydrogenase (sGDH) of bacterium Acinetobactor calcoaceticus. Because PQQ is structurally similar to photochemically reactive phenanthrene-9, 10-dione, illumination is expected to enhance PQQ's oxidation reactions. Our results have confirmed this hypothesis and expanded the scope of PQQ's substrates under light. PQQ is able to form a complex with another cofactor of the native apoprotein, Ca²⁺, which also serves as a catalyst for the oxidation reactions. UV spectrum indicated complex formation between PQQ and such bivalent metal ions as Cd²⁺, Mg²⁺, Mn²⁺, and Sr²⁺. We also study the catalytic effect of the latter complexes on PQQ's reactions.