Flavins studies

The redox properties of eight different N,N,N-l,3,5-triaIkylated flavins and their activity as redox catalysts for the oxidation of sulfides were studied [49]. The redox potentials ( b) were determined by cyclic voltammetry, and for the eight flavins studied Eg varied from —0.414 to 0.162 V. There was a linear free-... 

Oxidative substitutions at ring junction positions in various tetrahydro-5-deaza-pterins (79JA6068) and -flavins (77JA6721) have been studied, e.g. to give (13), and the oxidation-reduction reactions of 5-deazaflavins (e.g. 78CL1177, 80CPB3514) across the 1,5-positions, e.g. (19) (20), are involved in their co-enzymic role in enzymic oxidations (see Section... 

Puget, K., and Michelson, A. M. (1972). Studies in bioluminescence. VII Bacterial NADH flavine mononucleotide oxidoreductase. Biochimie 54 1197-1204. 

A successful case study for asymmetric nitrogen oxidation was reported for a series of (hetero)aromatic tertiary amines. High diastereoselectivity was observed for the enzyme-mediated oxidation of S-(—)-nicotine by isolated CHMOAdneto to give the corresponding ds-N-oxide [215]. The stereoselectivity of this biooxidation was complementary to the product obtained by flavin M O (FM O) from human li ver (trows-selective [216]) as well as unspecific oxidations by FMOs from porcine and guinea pig liver. 

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... 

This key enzyme of the dissimilatory sulfate reduction was isolated from all Desulfovibrio strains studied until now 135), and from some sulfur oxidizing bacteria and thermophilic Archaea 136, 137). The enzymes isolated from sulfate-reducing bacteria contain two [4Fe-4S] clusters and a flavin group (FAD) as demonstrated by visible, EPR, and Mossbauer spectroscopies. With a total molecular mass ranging from 150 to 220 kDa, APS reductases have a subunit composition of the type 012)32 or 02)3. The subunit molecular mass is approximately 70 and 20 kDa for the a and )3 subunits, respectively. Amino-acid sequence data suggest that both iron-sulfur clusters are located in the (3 subunit... 

Hartmann S, C Hultschig, W Eisenreich, G Fuchs, A Bacher, S Ghisla (1999) NIH shift in flavin-dependent monooxygenation mechanistic studies with 2-aminobenzoyl-CoA monooxygenase/reductase. Proc Natl Acad USA 96 7831-7836. 

Whatever the reason may be behind the strict necessity to deprotonate the flavin donor, the reduced and deprotonated flavin was established in these model studies to be an efficient electron donor, able to reduce nucle-obases and oxetanes. In the model compounds 1 and 2 the pyrimidine dimer translates the electron transfer step into a rapidly detectable chemical cycloreversion reaction [47, 48], Incorporation of a flavin and of a cyclobutane pyrimidine dimer into DNA double strands was consequently performed in order to analyse the reductive electron transfer properties of DNA. 

Fig. 5 Flavin-capped and dimer containing DNA hairpin for excess electron transfer studies through DNA...

The feature of xanthine oxidase which is no doubt of the greatest chemical interest, is the presence of several non-protein components. Much effort has been expended in attempting to elucidate the respective roles of iron, flavin and molybdenum in the various enzyme catalysed reactions. Numerous studies of the iron constituent have been made of late (45, 46, 47, 48, 49, 50), it having been found to be of the iron-sulphur (51 a, 51 b) type. Neither iron (19) nor molybdenum (31) can be removed reversibly from the enzyme, though the FAD can be (52, see below). 

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... 

Furushima, R., Kita, K., Takamiya, S., Konishi, K., Aoki, T. and Oya, H. (1990) Structural studies on three flavin-interacting regions of the flavoprotein subunit of complex II in Ascaris suum mitochondria. FEBS Letters 263, 325-328. 

The possible mechanisms of inhibition of flavin by (—)-deprenyl, as an irreversible acetylenic inhibitor, were studied by ab initio methods with the 6-31G basis set using simplified model compounds, 3-formyl-2-imino-l-hydroxypyrazine, and propargylamine. The formation of two energetically stable cyclic adducts, the 0,N adduct 286 and a C,N adduct, was shown <1999THA147>. 

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