1. Hydrogenase enzymes

2. Hydrogenases Anaerobic bacteria: -production of H 2 during fermentation of sugars -the use of H 2 in the reduction of CO 2 to methane or other compounds. -parallel hydogenase function of nitrogenase enzymes -H 2 as biological energy source

3. 1. Iron hydrogenases

5. F cluster - Fe 4 S 4 +/2+ type, and ESR signal characteristic to the S=1/2 spin state in the reduced state of the enzyme. H cluster – hydrogen activation site; its oxidised form is ESR active. 1. Iron hydrogenases

6. The redox potential of the F/S clusters of the C. Pasteurianum bacterium at pH ~ 8, and the mechanism of the hydrogenase II: Both H 2 oxidation and production of H 2 22Fe: 4F, 1H H 2 -oxidation 14Fe: 2F (F,F’), 1H 1. Iron hydrogenases

7. The H cluster 1. Iron hydrogenases X-ray structure of the hydrogenase I enzyme of the C. Pasteurianum bacterium [Peters, J. W., Lanzilotta, W. N., Lemon, B. J. & Seefeldt, L. C. (1998) Science, 282, 1853–1858.]

8. Schematic pictures of the hydrogen production and oxidation (A), and the direction of the electron transfer during reduction of the proton and oxidation of the H 2 (B). 1. Iron hydrogenases

9. Schematic drawing of the mechanism of the hydrogenase enzyme +H 2 2. Nickel-iron hydrogenases

10. X-ray structure of the NiFe hidrogenase enzyme of D. Gigas bacterium. On the right side the active centre of the enzyme is depicted, X = Fe, L1– 3 = CN – and CO ligands, positions I and II indicate the H 2 binding sites. 2. Nickel-iron hydrogenases

11. Bioinorganic chemistry of the C1 compounds

12. Main steps of reduction of CO 2 to methane, and the necessary cofactors. Binding sites of the C1 compounds are indicated by arrows in the formula of the cofactors.

13. Assumed mechanism of the methyl-coenzyme M reductase enzyme 1. Methyl coenzyme M reductase

14. Structure of F430 coenzyme 1. Methyl coenzyme M reductase

15. The role of nickel in the reaction: 1. Binding of the substrate thioether or thiol groups. 2. Cleavage of the C–S bond (see Raney-Ni as desulfurilation catalyst). 3. Short life methyl binding site. 4. Oxidativ link of the sulfur atoms to disulfid. 1. Methyl coenzyme M reductase

16. CO-dehydrogenase Acethyl-CoA-synthase 2. CO-dehydrogenase = CO-oxidoreductase = Acethyl-CoA-synthase

17. Mechanism of the acethyl coenzyme A-synthase enzyme 2. CO-dehydrogenase = CO-oxidoreductase = Acethyl-CoA-synthase

18. X-ray structure of the acethyl-coenzyme A synthase enzyme of the C. hydrogenoformans (A) and the schematic picture of the active centre with several bond lengths 2. CO-dehydrogenase = CO-oxidoreductase = Acethyl-CoA-synthase

19. Other redoxienzymes in biological processes 1. Transformation of nucleotides: ribonucleotide reductase enzymes

20. 1. Transformation of nucleotides: ribonucleotide reductase

21. X-ray structure of the active centre of class I (A) and III (B) bacterial RR enzymes

22. The dinuclear iron centre of ribonucleotide reductase enzyme of E. Coli 1. Transformation of nucleotides: ribonucleotide reductase

23. Schematic mechanism of the sMMO enzyme 2. Methane monooxygenase

24. 3. Oxotransferase enzymes Schematic structure of the molybdopterine cofactor

25. Probable mechanism of the sulfite-oxidase enzyme 3. Oxotransferase enzymes

26. 4. Alcohol-dehydrogenase enzymes

27. Structure and NADH binding site of the ADH enzyme of Pseudomonas aeruginosa 4. Alcohol-dehydrogenase enzymes

28. Active centre (the substrate analogue ethyleneglycole is bound to the zinc(II) ion) of the ADH enzyme of Pseudomonas aeruginosa. Protein Science (2004), 13:1547–1556. 4. Alcohol-dehydrogenase enzymes