Flavin, generally

Lu, C. Y. Lui, Y.Y. (2002). Electron transfer oxidation of tryptophan and tyrosine by triplet states and oxidized radicals of flavin sensitizers a laser flash photolysis study. Biochimica et Biophysica Acta (BBA) - General Subjects, Vol. 1571, No.l, (May 2002), pp. 71-76, ISSN 0304-4165... 

It must be realised however (as indeed it was at the time of these experiments (53)) that the use of such studies to determine the sequence, has certain limitations. The first limitation is that nothing can be said about the role of species not detectable by EPR, such as fully reduced flavin. Secondly and more generally, it has to be assumed for both the oxidizing and reducing substrates, that each reacts with only one of the... 

Fig. 21. Top The general Jablonski diagram for the flavin chromophore. The given wavelengths for absorption and luminescence represent crude average values derived from the actual spectra shown below. Due to the Franck-Condon principle the maxima of the peak positions generally do not represent so-called 0 — 0 transitions, but transitions between vibrational sublevels of the different electronically excited states (drawn schematically). Bottom Synopsis of spectra representing the different electronic transitions of the flavin nucleus. Differently substituted flavins show slightly modified spectra. Absorption (So- - S2, 345 nm S0 -> Si,450nm 1561) fluorescence (Sj — S0) 530 nm 156)) phosphorescence (Ty Sq, 605 nm 1051) triplet absorption (Tj ->Tn,...

Enzymes containing amino acid radicals are generally associated with transition metal ions—typically of iron, manganese, cobalt, or copper. In some instances, the metal is absent it is apparently replaced by redox-active organic cofactors such as S -adenosylmethionine or flavins. Functionally, their role is analogous to that of the metal ion in metalloproteins. 

Substrate Spectra. Photodecomposition of five insecticidal chemicals stimulated by protease-liberated flavoprotein was studied and results are shown in Tables II and III and Figures 3, 4 and 5. Generally the flavoprotein(s) was significantly more active in stimulating the photodegradation process in the absence than in the presence the flavin cofaggor (FMN). 

So what does riboflavin do As such riboflavin does nothing. Like thiamine, riboflavin must undergo metabolic change to become effective as a coenzyme. It fact, it undergoes two reactions. The first converts riboflavin to riboflavin-5-phosphate (commonly known as flavin adenine mononucleotide, FMN), about which we will say no more, and the second converts it to flavin adenine dinucleotide, FAD. The flavins are a class of redox agents of very general importance in biochemistry. FAD is the oxidized form and FADH2 is the reduced form. ... 

The flavin monooxygenases (FMOs) are a family of five enzymes (FMO 1-5) that operate in a manner analogous to the cytochrome P450 enzymes in that they oxidize the drug compound in an effort to increase its elimination. Though they possess broad substrate specificity, in general they do not play a major role in the metabolism of drugs but appear to be more involved in the metabolism of environmental chemicals and toxins. 

Riboflavin synthase catalyzes the dismutation of 8-D-ribityl-6,7-dimethyllumazine to form the flavin ring system and the general features of the mechanism of this reaction have been known for some time. Recent X-ray structural studies of the enzyme from archaeal organisms such as methanobacteria have shown that the chemical mechanism of action is similar to that of enzymes from eubacteria and eukaryotes although the structures of the enzymes differ greatly <2006JBC1224>. 

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