修飾シクロデキストリンによる電子伝達系モデル

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β-Cyclodextrin-nicotinamides reduce a substrate upon complex formation, simulating NADH-dependent enzymes which catalyzes the reductions within the ternary (enzyme-coenzyme-substrate) complexes. The newly synthesized β-cyclodextrin-nicotinamides (4, 7) and (10) have a nicotin amide group on the secondary hydroxy-side of β-cyclodextrin, in an axial configuration for (4), equatorial for (7), and axial configuration with amide linkage for (10). The corresponding reduced forms can reduce ninhydrin with large rate enhancements (7) relative to NADH. They also show enzyme-like saturation kinetics in the reduction of ninhydrin, which indicates that the reaction involves complex formation. The reduction of flavins by NAD (P) H is an important step in the natural respiratory electron transport chain.<BR>This paper demonstrates the non-enzymatic reductions of cytochrome c in aqueous solutions, which are initiated by β-cyclodextrin-dihydronicotinamides and mediated by a riboflavin, oxazine-, diazine-, thiazine- and indophenol-dyes. Rate enhancement associated with complex formation between cyclodextrin-dihydronicotinamides and mediators was demonstrated by the inhibition kinetics and Michaelis-Menten type kinetics.
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