Hydrogenase enzymes

Hydrogenases

Anaerobic bacteria:

-production of H2 during fermentation of sugars

-the use of H2 in the reduction of CO2 to methane or other compounds.

-parallel hydogenase function of nitrogenase enzymes

-H2 as biological energy source

1. Iron hydrogenases

1. Iron hydrogenases

F cluster - Fe4S4+/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

The redox potential of the F/S clusters of the C. Pasteurianum bacterium at pH ~ 8, and the mechanism of the hydrogenase II:

Both H2 oxidation and production of H2

22Fe: 4F, 1HH2-oxidation14Fe: 2F (F,F’), 1H

1. Iron hydrogenases

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.]

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 H2 (B).

FeI FeI

e-

e-

Fe0 FeI

FeII FeI

H-

FeII FeI

H2 H2

e-e-

H+H+

H+

H+

H

H

0

H+

OCFeFe

SS S 4Fe4S

CN

Cys

COCOCN

e-

e-

OCFeFe

SS S 4Fe4S

CN

Cys

COCOCN

H

H

II

1. Iron hydrogenases

Schematic drawing of the mechanism of the hydrogenase enzyme

+H2

2. Nickel-iron hydrogenases

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 H2 binding sites.

2. Nickel-iron hydrogenases

Bioinorganic chemistry of the C1 compounds

Bioinorganic chemistry of the C1 compounds

Main steps of reduction of CO2 to methane, and the necessary cofactors. Binding sites of the C1 compounds are indicated by arrows in the formula of the cofactors.

Assumed mechanism of the methyl-coenzyme M reductase enzyme

1. Methyl coenzyme M reductase

Structure of F430 coenzyme

COO-

N

N N

N

HN

O

O

H

H3C

H

H

CH3

COO-

COO-

-OOC

H2NOC

COO-

Ni+

1. Methyl coenzyme M reductase

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

CO-dehydrogenase

Acethyl-CoA-synthase

2. CO-dehydrogenase = CO-oxidoreductase

= Acethyl-CoA-synthase

Mechanism of the acethyl coenzyme A-synthase enzyme

2. CO-dehydrogenase = CO-oxidoreductase

= Acethyl-CoA-synthase

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

BA

2. CO-dehydrogenase = CO-oxidoreductase

= Acethyl-CoA-synthase

Other redoxienzymes in biological processes

1. Transformation of nucleotides: ribonucleotide reductase enzymes

1. Transformation of nucleotides: ribonucleotide reductase

1. Transformation of nucleotides: ribonucleotide reductase

A B

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

The dinuclear iron centre of ribonucleotide reductase enzyme of E. Coli

1. Transformation of nucleotides: ribonucleotide reductase

Schematic mechanism of the sMMO enzyme

2. Methane monooxygenase

3. Oxotransferase enzymes

Schematic structure of the molybdopterine cofactor

Probable mechanism of the sulfite-oxidase enzyme

3. Oxotransferase enzymes

4. Alcohol-dehydrogenase enzymes

Structure and NADH binding site of the ADH enzyme of Pseudomonas aeruginosa

4. Alcohol-dehydrogenase enzymes

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