Photochemical Coenzyme Regeneration in an Enzymatically Active Optical Material

Abstract

The photoinduced electron transfer between immobilized thionine and the dinucleotide enzyme cofactors NADH and NADPH in a SiO 2 sol-gel matrix is reported. The electron-transfer quenching of thionine luminescence is used to monitor the rate of NADPH oxidation. Using Stern-Volmer quenching curves, the quenching rates in the silica matrix are 1 to 2 orders of magnitude smaller than those in solution. The rate constants for oxidation of NADPH by thionine were measured to be 9.8((2.9) × 10 -3 s -1 in solution and 8.8((1.0) × 10 -4 s -1 in the gel. Within the silica matrix, the photoinduced oxidation of NADPH is combined with the enzymatic reaction of isocitrate dehydrogenase, which uses the oxidized cofactor, NADP + , as an electron acceptor in the oxidation of isocitrate. The encapsulated isocitrate dehydrogenase is active with a Michaelis-Menten constant, K M , of 3 µM and a k cat of 0.67 µM/s per mg enzyme . Because optical sensors use NADPH fluorescence as an indicator of the presence and relative concentration of enzyme substrate, the successful demonstration of photoinduced regeneration of NADP + makes possible continuous monitoring by the family of dehydrogenase enzymes.

Photobiocatalysis: Activating Redox Enzymes by Direct or Indirect Transfer of Photoinduced Electrons

“…[123] Photosensitization can offer the potential required for the oxidation of NAD(P)H. Dunn et al reported the light-driven oxidation of NAD(P)H using thionine-doped SiO 2 . [124] Photosensitized thionine could oxidize NAD(P)H at the TOFof35.28 h À1 in afree solution and 3.17 h À1 in the SiO 2 gel, while the reduced thionine converted O 2 to H 2 O ( Figure 11 A). As tudy by Moore et al reported aP EC platform consisting of a5 -(4-carboxyphenyl)-10,15,20-tris(4-methyl-pheny1)porphyrin-TiO 2 photoanode and aP tc athode, which demonstrated photooxidation of NADH coupled with H 2 production.…”

Compartmentalized Nanocomposite for Dynamic Nitric Oxide Release

“…[48][49][50][51] This difference is often attributed to diffusion limitations or multiple populations of molecules in different regions of the porous matrix. In this case the photochemical production of NO from SNAP is not dependent on bimolecular collisions and should not be reduced by diffusion limitations.…”

Photobiokatalyse: Aktivierung von Redoxenzymen durch direkten oder indirekten Transfer photoinduzierter Elektronen

“…[118] 4. [124] Photosensibilisiertes Thionin in freier Lçsung war in der Lage,NAD(P)H mit einer TOFvon 35.28 h À1 zu katalysieren, während die TOFi nd em SiO 2 -Gel 3.17 h À1 betrug.D abei vermittelte reduziertes Thioin die Reduktion von O 2 zu H 2 O (Abbildung 11 A). B. durch NAD(P) + ]stellt einen vielversprechenden Ansatz in der nachhaltigen Syntheschemie dar.S oi st beispielsweise die Oxidation von Alkoholen eine Schlüsselreaktion in der organischen Synthesechemie.…”

“…[123] Das zur Oxidation von NAD(P)H nçtige Potential kann durch Photosensibilisation erreicht werden. So berichteten Dunn et al von der photogetriebenen Oxidation von NAD(P)H unter Einsatz von Thionin-dotiertem SiO 2 [124]. Photosensibilisiertes Thionin in freier Lçsung war in der Lage,NAD(P)H mit einer TOFvon 35.28 h À1 zu katalysieren, während die TOFi nd em SiO 2 -Gel 3.17 h À1 betrug.D abei…”