Bacteria flavins

In bacteria, flavin adenine dinucleotide (FAD) is the prosthetic group of the photolyases that catalyze reductive repair of light-induced pyrimidine dimers in DNA. Riboflavin is the light-emitting molecule in some bioluminescent fungi and bacteria, and is the precursor for synthesis of the dimethylbenzimidazole ring of vitamin B12 (Section 10.7.3). 

If the luciferase sample solution contains a flavin-reductase, luciferase activity can be measured by the addition of FMN and NADH, instead of FMNH2. In this case, the turnover of luciferase takes place repeatedly using the FMNH2 that is enzymatically generated thus, the luminescence reaction continues until aldehyde or NADH is exhausted. A crude luciferase extracted from luminous bacteria usually contains a flavin-reductase. 

Duane, W., and Hastings, J. W. (1975). Flavin mononucleotide reductase of luminous bacteria. Mol. Cell. Biochem. 6 53-64. 

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... 

Russ R, J Rau, A Stolz (2000) The function of cytoplasmic flavin reductases in the reduction of azo dyes by bacteria. Appl Environ Microbiol 66 1429-1434. 

Based on the previous publications, azo dye can be reduced by azoreductase-catalyzed reduction under anaerobic conditions. But still there is a speculation whether bacterial flavin reductases are responsible for the azo reductase activity observed with bacterial cell extracts. In a published report, it is reported that flavin reductases are indeed able to act as azo reductases [24]. Bacteria produce extracellular oxidative enzymes, which are relatively nonspecific enzymes catalyzing the oxidation of a variety of dyes. It was reported that so many diverse groups of bacteria play a role in decolorization. It has been also reported that mixed microbial community could reduce various azo dyes, and members of the y-proteabacteria and sulfate reducing bacteria (SRB) were found to be prominent members of mixed bacterial population by using molecular methods to determine the microbial population dynamics [1],... 

The azo reductases in aerobic bacteria were found to be existent when azoreductases from obligate aerobic bacteria were isolated and characterized from strains K22 and KF46 and were shown to be flavin-free after purification, characterization, and comparison 364, 362,363. These intracellular azoreductases showed high specificity to dye structures. Furthermore, Blumel and Stolz cloned and characterized the genetic code of the aerobic azo reductase from Pagmentiphaga... 

From the biological point of view, the effect of anaerobiosis has been characterized in purely anaerobic, facultative anaerobic, and aerobic bacteria, in yeasts, and in tissues from higher organisms [6-12], From these studies it can be deduced that almost every azo compound can be biologically reduced under anaerobic conditions [4]. Reduced flavins are produced by cytosol flavin-dependent reductases [6, 13], while quinone reductase activity located in the plasma membrane [14] and extracellular azo reductase activities [9, 15] were also observed. 

All bacteria where nitrate ester degradation has been characterized have very similar enzymes. The enzymes eatalyze the nicotinamide cofactor-dependent reductive eleavage of nitrate esters that produces alcohol and nitrite. Purification of the PETN reduetase from Enterobacter cloacae yielded a monomerie protein of around 40 kilo Daltons, which required NADPH as a co-faetor for aetivity. Similar enzymes were responsible for the nitrate ester-degrading activity in Agrobacterium radiobacter (Snape et al. 1997) - nitrate ester reductase - and in the strains of Pseudomonas fluorescens and Pseudomonas putida (Blehert et al. 1999) - xenobiotic reduetases . All utilize a non-covalently bound flavine mononucleotide as a redox eofactor. 

Rebeccamycin is an antitumor or antibiotic agent isolated from bacteria " and contains a maleimide indolocarbazole framework. The Trp units in this molecule are chlorinated at the C-7 position and a flavin-dependent halogenase was identified as the enzyme that carries out this chlorination (Scheme 10). " There are many other halogenating enzymes known in the literature and these enzymes are responsible for the syntheses of metabolites containing bromine, chlorine, and fluorine. ... 

Three other proteins with similar domain structure as that of FprA were reported in other bacteria (WasserfaUen et al. 1995 Gomes et al. 1997, 2000). The recombinant CthFprA and CthHrb, overexpressed in E. coli, were purified and characterized. Both FprA and Hrb were found to be present as dimers. Metal/cofactor analysis of the purified proteins revealed the presence of 2 mol each of iron and flavin (FMN) per mole dimer of Hrb and 4 mol of iron and 2 mol FMN per mole dimer of FprA. The EPR spectra of the purified proteins indicated that iron is present in a di-iron center in FprA and as a Fe(Cys)4 cluster in Hrb. 

Notably, nitrile-degrading enzymes (e.g. nitrilase that converts the CN group to carboxylic acid, and nitrile hydratase that produces an amide function) have been described, and they co-exist with aldoxime-degrading enzymes in bacteria (Reference 111 and references cited therein). Smdies in this area led to the proposal that the aldoxime-nitrile pathway, which is implemented in synthesis of drugs and fine chemicals, occurs as a natural enzymic pathway. It is of interest that the enzyme responsible for bacterial conversion of Af-hydroxy-L-phenylalanine to phenacetylaldoxime, an oxidative decarboxylation reaction, lacks heme or flavin groups which are found in plant or human enzymes that catalyze the same reaction. Its dependency on pyridoxal phosphate raised the possibility that similar systems may also be present in plants . 

Yamasaki, I. 1941. Flavin formation by the acetone-butyl alcohol bacteria. IV. Biochem. Z. 307, 431-441. (German)... 

When taken up by the body, riboflavin is converted into its coenzyme forms (Chapter 25) and any excess is quickly excreted in the urine. Urine also contains smaller amounts of metabolites. The ribityl group may be cut by the action of intestinal bacteria acting on riboflavin before it is absorbed. The resulting 10-hydroxyethyl flavin may sometimes be a major urinary product.c d The related 10-formylmethyl flavin is also excreted,0 as are small amounts of 7a- and 8a- hydroxyriboflavins, apparently formed in the body by hydroxylation. These may be degraded farther to the 7a- and 8a- carboxylic acids of lumichrome (riboflavin from which the ribityl side chain is totally missing).6 A riboflavin glucoside has also been found in rat urine.f... 

This unique redox catalyst links the oxidation of H2 or of formate to the reduction of NADP+229 and also serves as the reductant in the final step of methane biosynthesis (see Section E) 228 It resembles NAD+ in having a redox potential of about -0.345 volts and the tendency to be only a two-electron donor. More recently free 8-hydroxy-7,8-didemethyl-5-deazaribo-flavin has been identified as an essential light-absorbing chromophore in DNA photolyase of Methanobacterium, other bacteria, and eukaryotic algae.230 Roseoflavin is not a coenzyme but an antibiotic from Streptomyces davawensisP1 Many synthetic flavins have been used in studies of mechanisms and for NMR232 and other forms of spectroscopy. 

If an enzyme binds a flavin radical much more tightly than the fully oxidized or reduced forms, reduction of the flavoprotein will take place in two one-electron steps. In such proteins the values of E° for the two steps may be widely separated. The best known examples are the small, low-potential electron-carrying proteins known as flavodoxins.266 269a These proteins, which carry electrons between pairs of other redox proteins, have a variety of functions in anaerobic and photosynthetic bacteria, cyanobacteria, and green algae. Their functions are similar to those of the ferredoxins, iron-sulfur proteins that are considered in Chapter 16. 

Luminescent bacteria all appear to obtain light from a riboflavin-5 -phosphate dependent oxygenase, which converts a long-chain aldehyde (usually n-tetradecanal) to a carboxylic acid (Eq. 23-47). Here FH2 is the riboflavin 5 -P, which is thought to be supplied by a flavin reductase.6793... 

Some bacteria, e.g., Pseudomonas putidap1 degrade L-lysine with a flavin-dependent oxygenase (Eq. 18-41) to 8-aminovaleramide ... 

Components of the electron transport chain in bacteria have been shown to include b- and c-type cytochromes, ubiquinone (fat-soluble substitute quinone, also found in mitochondria), ferredox (an enzyme containing nonheme iron, bound to sulfide, and having the lowest potential of any known electron-canying enzyme) and one or more flavin enzymes. Of these a cytochrome (in some bacteria, with absorption maximum at 423.5 micrometers, probably Cj) has been shown to be closely associated with the initial photoact. Some investigators were able to demonstrate, in chromatium, the oxidation of the cytochrome at liquid nitrogen temperatures, due to illumination of the chlorophyll. At the very least this implies that the two are bound very closely and no collisions are needed for electron transfers to occur. 

Two different enzyme systems have been described, one uses cytochrome P-450 to activate oxygen whereas the other employs flavin adenine dinucleotide (FAD). Both the cytochrome P-450 and the flavin monooxygenase systems have broad substrate specificities and oxidize and oxygenate a variety of organic nitrogen or sulfur compounds. The enzymes have a widespread distribution and have been detected in animals, plants, fungi and bacteria. Their function appears to be primarily one of detoxification of xenobiotics. Microbial enzymes... 

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