Trimethylamine dehydrogenase

In the same study it was also shown that at least one proton is involved in the reaction in the pH range 6-8, controlling intramolecular electron transfer, whereas at least two protons are involved between pH 8 and 10, controlling formation of the spin-interacting state. The results indicate that at least three protonation/deprotonation events are associated with intramolecular electron transfer and formation of the spin-interacting state, with estimated pKa values of 6.0, 8.0 and 9.5. These pKa values were attributed to the flavin hydroquinone, flavin radical, and an undesignated basic group on the protein, respectively. 

In a previous study at P- and X-band, the temperature dependence of the magnetically coupled spectrum and its analysis based on a triplet-state spin-Hamiltonian were used to propose the range (0.8-100 cm ) for the parameter Jo of the isotropic exchange interaction JoSa Sb, but neither the magnitude of Jo nor its sign could be further specified.  

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Lim, L.W., et al. Three-dimensional structure of the iron-sulfur flavoprotein trimethylamine dehydrogenase at 2.4 A resolution. J. Biol. Chem. 261 15140-15146, 1986. 

Like PDR, trimethylamine dehydrogenase (TMADH) from Methylo-philus methylotrophus W3A1 provides an example of a system in which an iron-sulfur center, in this case a [4Fe-4S] cluster, interacts... 

Foumel, A., Gambarelli, S., Guigliarelli, B., More, C., Asso, M., Chouteau, G., Hille, R., and Bertrand, P. 1998. Magnetic interactions between a 4Fe-4S l+ cluster and a flavin mononucleotide radical in the enzyme trimethylamine dehydrogenase a high-field electron paramagnetic resonance study. Journal of Chemical Physics 109 10905-10913. 

R. Hille and R.F. Anderson, Coupled electron/proton transfer in complex flavoproteins — solvent kinetic isotope effect studies of electron transfer in xanthine oxidase and trimethylamine dehydrogenase. J. Biol. Chem. 276, 31193-31201 (2001). 

There is, up to now, one exception known to the four kinds of the above mentioned covalent linkages. The prosthetic group of trimethylamine dehydrogenase is linked via the C(6)-atom of the flavin to a cysteinyl residue (Scheme 3, (5)). As mentioned above the less reactivity of C(6) of flavin as compared to that of CH3(8) requires probably some chemical modification of the prosthetic by biologicai means prior to covalent attachment. The C(6)-S-Cysteinyl flavin was synthesized recently starting with 6-nitro flavin which was subsequently reduced to the amino derivative and transformed to the corresponding bromo derivative via diazotation. Reaction of the bromo derivative with cysteine gave the desired 6-S-Cysteinyl derivative... 

The transition flavoquinone-flavosemiquinone seems not to be useful in flavoproteins catalysis. Only trimethylamine dehydrogenase electron-acceptor flavoprotein, isolated from bacterium W3A1 , makes probably use of this shuttle 240,241) -j-jjg enzyme forms a very air-stable anionic flavosemiquinone. 

The properties of the semiquinone from of the ETF isolated from the methylotrophic bacterium resemble those of the bacterial flavodoxins with the exception that flavodoxins form neutral semiquinones whereas this ETF forms an anionic semiquinone. Nearly quantitative anionic semiquinone formation is observed either in the presence of excess dithionite or when excess trimethylamine and a catalytic amount of trimethylamine dehydrogenase are added. Of interest is the apparent stability of the anionic semiquinone towards oxidation by O2 but not to oxidizing agents such as ferricyanide. This appears to be the first example of an air-stable protein-bound anionic flavin semiquinone. Future studies on the factors involved in imparting this resistance to O2 oxidation by the apoprotein are looked forward to with great interest. 

In contrast to the flavin oxidases, flavin dehydrogenases pass electrons to carriers within electron transport chains and the flavin does not react with 02. Examples include a bacterial trimethylamine dehydrogenase (Fig. 15-9) which contains an iron-sulfur duster that serves as the immediate electron acceptor167 169 and yeast flavocytochrome b2, a lactate dehydrogenase that passes electrons to a built-in heme group which can then pass the electrons to an external acceptor, another heme in cytochrome c.170-173 Like glycolate oxidase, these enzymes bind their flavin coenzyme at the ends of 8-stranded a(i barrels similar... 

These include 8a-(Ne2-histidyl)-FMN,221 8a-(N81-histidyl)-FA D,222 8a-(0-tyrosyl-FAD),223 and 6-(S-cysteinyl)-riboflavin 5 -phosphate, which is found in trimethylamine dehydrogenase (Fig. 15-9).224 An 8-hydroxy analog of FAD (-OH in place of the 8-CH3)... 

Iron-sulfur clusters are found in flavoproteins such as NADH dehydrogenase (Chapter 18) and trimethylamine dehydrogenase (Fig. 15-9) and in the siroheme-containing sulfite reductases and nitrite reductases.312 These two reductases are found both in bacteria and in green plants. 

Trimethylamine dehydrogenase 782, 784s Trimethylarsonium lactic acid, 387s Trimethyllysine... 

Loechel et al. [20] Trimethylamine Fish Trimethylamine dehydrogenase (TMADH) (Dimethylamine) methylene ferrocene (DMAMFe)... 

C. Loechel, A. Basran, J. Basran, N. S. Scrutton and E. A. Hall, Using trimethylamine dehydrogenase in an enzyme linked amperometric electrode. Part 1. Wild-type enzyme redox mediation, Analyst, 128(2) (2003) 166-172 Part 2. Rational design engineering of a wired mutant, Analyst, 128(7) (2003) 889-898. 

A barrels nearly circular small helix between /7-strand 8 and a-helix 8 domain covering N-terminus of the barrel glycolate oxidase, trimethylamine dehydrogenase... 

Trimethylamine dehydrogenase is an iron-sulfur flavoprotein found in the methylotrophic bacterium Methylophilus methylotrophus W3A1. It catalyzes the oxidative N-demethylation of trimethylamine by water with formation of dimethylamine and formaldehyde (Steenkamp and Mallinson, 1976). The protein is a symmetrical dimer consisting of 166kDa subunits (Kasprzak et al., 1983 Lim et al., 1982). Each subunit contains one 4Fe-4S center and one FMN cofactor. The latter is bound covalently through the 6... 

FIGURE 10. Stereo diagram of domain 1 of trimethylamine dehydrogenase. Residues ln371 are shown. Helices aj-ttg of the PgtXg TIM barrel are indicated. The iron sulfur cluster-binding loop consisting of an a-helix and a P-strand is located at the end of helix Og. 

Lim, L. W., Mathews, F. S., and Steenkamp, D. J., 1982, Crystallographic study of the iron-sulfur flavoprotein trimethylamine dehydrogenase from the bacterium W3A1. J. Mol. Biol. 162 8699876. 

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