Enzymes flavo

In the field of enzymatic oxidations, especially the class of flavo enzymes with bound FAD as cofactor is interesting for synthetic applications. The... 

Thus, it was shown that flavo enzymes and comparable systems can be used for synthetic applications in a continuous process under anaerobic reactivation of the prosthetic group in the electrochemical enzyme membrane reactor [46, 50],... 

A synthetically interesting synthetic application of flavo enzymes using ferrocene-boronic acid as mediator [134] has been described for the transformation of /7-hydroxy-toluene (p-cresol) to /7-hydroxybenzaldehyde, which is catalyzed by the enzyme p-cresolmethyl hydroxylase (PCMH) from Pseudomonas piitida. This enzyme is a flavocy-tochrome containing two FAD and two cytochrome c prosthetic groups. To develop a continuous process using ultrafiltration membranes to retain the enzyme and the mediator, water-soluble polymer-bound ferrocenes [26-31,135] (Scheme 3) have been applied as redox catalysts for the application in batch electrolyses or in combination with an electrochemical enzyme membrane reactor (see Fig. 24) [26-31,135] with excellent results. 

Figure 4.7. Structures used by Reichenbach-Klinke et al. [62] as agents to reduce riboflavin tetraacetate as a model of the flavin-nicotinamide redox interaction in flavo-enzymes. The second-order rate constants shown are approximate values for the redox reaction at 50 pM concentrations of each reactant in aqueous solution at pH 7.4 and 25 °C. The first-order rate constants for compounds with a Zn-center were obtained...

Kelner, M. J., Bagnell, R., Hale, B., and Alexander, N. M. (1988). Methylene blue competes with paraquat for reduction by flavo-enzymes resulting in decreased superoxide production in the presence of heme proteins. Arch. Biochem. Biophys. 262, 422-426. 

Chiral iminium ions can serve as mimics of flavo-enzymes in that they catalyze asymmetric oxygen transfer from dihydrogen peroxide or persulfate... 

There are two additional pyridine nucleotide-requiring flavo-enzymes for which the metal ion requirements are unknown 212) (see 9 and 10 below). Both cleave the pyridine nucleus at the bond adjacent to the hydroxyl substituent. However, the similarity with phenol-cleaving dioxygenases is fortuitous. The reaction course derives from the inherent instability of the intermediate cw-diols rather than from a similar catalytic mechanism. Two different mechanisms have been advanced. The first, which is based on kinetic studies 213, 214), consists of reduction of the substrate to its anion followed by its oxygenation (eq. 51). The... 

This flavo-enzyme contains one gram atom of non-heme ferric ion per mole of enzyme. Both atoms from molecular oxygen are incorporated into the acetone products (226). Arguments in favor of the intermediacy of superoxide ion have been suggested (75). Nevertheless, a carbanionic mechanism is equally feasible. The softened nitrocarbanion (77), on oxygenation, gives the hydroperoxide ion (78) which reacts with the parent molecule (79) to give the peroxide (80). Elimination of a molecule of nitrous acid yields the products (81) (Scheme 34). 

The authors argue that flavin nitroxyl radical may play a role in flavo-enzyme chemistry and suggest that the nitroxyl radical intermediate may be derived from enzyme-bound flavin 4a-hydroperoxide. 

R.A. Copeland, S.P.A. Fodor, T.G. Spiro, Surface-enhanced Raman spectra of an active flavo enzyme glucose oxidase and riboflavin binding protein on silver particles. J. Am. Chem. Soc. 106, 3872 (1984)... 

Since the mid-2000s, biocatalysis has been demonstrated to be a very powerful tool for the preparation of optically active sulfoxides using mild conditions. Among all the biocatalysts employed for the preparation of chiral sulfoxides, in particular flavo-enzymes have proven their efficiency. Flavoprotein oxidases have been employed as... 

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