초록
<P>Recently, CO<SUB>2</SUB> utilization technology, including artificial photosynthesis, has received much attention. In this field, CO<SUB>2</SUB> is used as a feedstock for fuels, polymers and in other chemical processes. Of note are malic enzymes (MEs) which catalyze the reaction of malic acid to pyruvic acid and CO<SUB>2</SUB> with the co-enzyme NADP<SUP>+</SUP>, and catalyze the reverse reaction of pyruvic acid and CO<SUB>2</SUB> to malic acid with the co-enzyme NADPH. Thus, MEs are also an attractive biocatalyst for carbon-carbon bond formation from CO<SUB>2</SUB>. Studies of the visible light-induced malic acid production from pyruvic acid and CO<SUB>2</SUB> using an electron donor, a photosensitizer, an electron mediator, ferredoxin-NADP<SUP>+</SUP> reductase, NADP<SUP>+</SUP>, and ME have been reported. However, modification of these systems is required, as they are very complicated. In this study, the visible light-induced carbon-carbon bond formation from pyruvic acid and CO<SUB>2</SUB> with ME using the photoreduction of 1,1′-diphenyl-4,4′-bipyridinium salt derivatives as a novel electron mediator with water-soluble tetraphenylporphyrin tetrasulfonate (H<SUB>2</SUB>TPPS) in the presence of triethanolamine (TEOA) as an electron donor was developed. When a sample solution containing TEOA, H<SUB>2</SUB>TPPS, 1,1′-diphenyl-4,4′-bipyridinium salt derivative, pyruvic acid, and ME in CO<SUB>2</SUB>-saturated bis-tris buffer was irradiated, the major product was oxaloacetic acid. Thus, a visible light-induced photoredox system for carbon-carbon bond formation from CO<SUB>2</SUB> with ME using 1,1′-diphenyl-4,4′-bipyridinium salt derivative as an electron mediator was developed.</P>