Thiocapsa roseopersicina

EPR spectra and g values for the various states of the hydrogenase from Thiocapsa roseopersicina 64) are depicted in Fig. 4. These spectra are representative of those of the other NiFe hydrogenases. 

K. L. Kovdcs, Cs. Bagyinka (1990) Structural properties and functional states of hydrogenase from Thiocapsa roseopersicina. FEMS Microbiol. Rev., 87 407-412... 

G. Rakhely, A. Colbeau, J. Garin, P. M. Vignais, K. L. Kovacs (1998) Unusual gene organization of HydSL, the stable [NiFe] hydrogenase in the photosynthetic bacterium Thiocapsa roseopersicina. J. Bacterial., 180 1460-1465... 

The oxidation of hydrogen in fuel cells provides clean energy and water as the only byproduct. Application of hydrogenase for hydrogen electrode is able to improve the characteristics of the fuel cells. Thermostable hydrogenase from Thiocapsa roseopersicina is an appropriate catalyst for development of several systems for production and transformation of renewable energy based on molecular hydrogen. 

N. A. Zorin, B. Dimon, J. Gagnon, J. Gaillard, P. Carrier, P. M. Vignais (1996) Inhibition by iodoacetamide and acetylene of the H-D exchange reaction catalyzed by Thiocapsa roseopersicina hydrogenase. Eur. J. Biochem., 241 675-681... 

O. A. Zadvomy, N. A. Zorin, I. N. Gogotov (2000) The effect of metal ions on hydrogenase of purple sulfur bacterium Thiocapsa roseopersicina. Biokhimiya. (Russ.), 65 1525-1529... 

S. V. Morozov, E. E. Karyakina, N. A. Zorin, S. D. Varfolomeyev, S. Cosnier, A. A. Karyakin (2002) Direct and electrically wired bioelectrocatalysis by hydrogenase from Thiocapsa roseopersicina. Bioelectrochemistry, 55 169-171... 

Sulfide oxidation by phototrophic bacteria is catalyzed by c-type cytochromes, flavocytochromes and even cytochrome c complexes (see 4.2). A heat-labile cytochrome c-550 of Thiocapsa roseopersicina is responsible for the oxidation of sulfide. The end product is elemental sulfur and it is assumed that this cytochrome might also catalyze the reverse reaction by reducing the intracellularly stored elemental sulfur to sulfide (4.9V... 

Dihydrogen can be rather easily evolved with Systems 10-15 of Table 1, where, with PET across the membrane, the water-soluble radical cation MV+ is produced outside the vesicle. This radical cation can evolve dihydrogen from water in the presence of various catalysts. This was demonstrated by Tsvetkov et al. [262] for System 12 of Table 1. As a catalyst, the c water soluble hydrogenase from Thiocapsa roseopersicina was used or a heterogeneous rhodium-polymer catalyst [263]. The quantum yield of H2 production was comparable with the quantum yield of MV+ generation. 

Figure 2. EPR spectra from Thiocapsa roseopersicina hydrogenase obtained on samples used in XAS experiments at 77 K. The spectra are arranged in order of decreasing redox potential top to bottom. Forms A and B correspond to oxidized enzyme, SI is an EPR silent intermediate, form C is an active form of the enzyme that is also EPR-active, and R is the fully reduced enzyme. (Reproduced from reference 35. Copyright 1993 American Chemical Society.)...

Figure 12. V ENDOR spectra (35 GHz) of 4+ (A) taken at g = 2.208 and of the nonexchangeable protons in Thiocapsa roseopersicina hydrog-enase-form C (B) taken at g = 2.19.

Figure 14. EPR spectra o/Thiocapsa roseopersicina hydrogenase, Ni-C (top) and Ni-L (bottom). Spectra were taken at 77 K, at a microwave frequency of 9.62 GHz, a microwave power of 20 raW, and a modulation amplitude of 4 G.

Figure 15. 2H-ENDOR spectra of the solvent exchangeable protons associated with Thiocapsa roseopersicina hydrogenase in form C (A) and its photoproduct (B).

Figure 16. Ni K-edge XAS spectra obtained for Thiocapsa roseopersicina...

Another APS reductase of interest is that which has been isolated by Triiper and Roger (S84) from Thiocapsa roseopersicina. The enzyme is reported to have a molecular weight of 180,000 and to contain 1 mole of flavin (presumably FAD), 4 g-atoms of nonheme iron, 6 moles of labile sulfide, and 2 c-type hemes per mole. The spectral properties of the enzyme are shown in Fig. 43. It utilizes cytochrome c and ferricyanide as... 

Fig. 43. Absorption spectra of the purified APS reductase from Thiocapsa roseopersicina ox, oxidized enzyme red, enzyme reduced with 1 mg sodium dithionite per ml. From Triiper and Rogers (3S4).

Many biomolecules feature metal ions in a mixed donor set, and the area is intensively studied. As an example, the active site of the hydrogenase from thiocapsa roseopersicina features nickel in a mixed 0,N,S donor environment. Definition of the ligand donor set in biopolymers is not always facile, however, so they tend to be overlooked as examples of mixed donor ligands. There are some small biomolecule examples extant. 

Jonkers H. M., deBruin S., and vanGemerden H. (1998) Turnover of dimethylsulfoniopropionate (DMSP) by the purple sulfur bacterium Thiocapsa roseopersicina Mil ecological implications. FEMS Microbiol. Ecol. 27, 281-290. 

Visscher P. T. and Van Gemerden H. (1991) Photoautotrophic growth of Thiocapsa roseopersicina on dimethyl sulfide. FEMS Microbiol. Lett. 81, 247-250. 

---