Microperoxidase-11 functionalized electrodes:: an active monolayer interface for the electrocatalyzed reduction of CoII-protoporphyrin IX reconstituted myoglobin and for the generation of integrated protein electrodes for bioelectrocatalyzed hydrogenation of acetylenes

Microperoxidase-ll, MP-11, is assembled as a monolayer on an Au electrode. The resulting MP-11 monolayer electrode mediates the electrocatalyzed reduction of Co-II-protoporphyrin IX reconstituted myoglobin, Co-II-Mb. The electrocatalyzed reduction of Co-II-Mb proceeds via the formation of a complex between the MP-11 monolayer and Co-II-Mb. The association constant of the complex formed between MP-11 and Co-II-Mb is K-a = 1.6 x 10(5) M-1. Cross-linking of the complex formed between Co-II-Mb and the MP-11 monolayer with glutaric dialdehyde yields a stable integrated electrocatalytic electrode for the stereospecific hydrogenation of acetylenedicarboxylic acid to maleic acid (current yield is ca. 80%). The electrocatalyzed hydrogenation of acetylenedicarboxylic acid reveals an isotope effect, k(H)/k(D) approximate to 2.7, suggesting the insertion of the substrate to a Co-III-H species in the rate-limiting step of the hydrogenation process.