Oxidation of dihydronicotinamides by flavin in enzyme and model reactions. Old yellow enzyme and lumiflavin.

TL;DRAbstract

We have compared the flavin-catalyzed oxidation of [1,4]-dihydronicotinamides by Old Yellow Enzyme at pH 8.0 and 25°C with that of the model reaction involving lumiflavin under the same conditions.Anaerobic stopped flow experiments established the following scheme for both the model and enzyme reactions (F, and F,Hare oxidized and fully reduced flavin, respectively, and RH2 is N-propyl dihydronicotinamide, NADH, or NADPH)The species (F,-*RH2)=w exhibits long wavelength absorbance in all cases.Hydrogen abstraction from RHz, as demonstrated by deuterium kinetic isotope effects, occurs in the kz step in both model and enzyme reactions.The intermediate, therefore, is either a biradical,

Chat with Paper

AI Agents for this Paper