Kinetic properties of the periplasmic hydrogenase from Desulfovibrio desulfuricans NCIMB 8372 and use in photosensitized H2-production
✍ Scribed by Lars H. Eng; Mona B.-M. Lewin; Halina Y. Neujahr
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2007
- Tongue
- English
- Weight
- 711 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0268-2575
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✦ Synopsis
Abstract
The periplasmic hydrogenase (hydrogen: ferricytochrome‐c~3~ oxido‐reductase EC 1.12.2.1) from Desulfovibrio desulfuricans (NCIMB 8372) was isolated and the catalytic properties of the enzyme determined with different electron mediators.
In the direction of H~2~‐oxidation with the physiological electron mediator cytochrome c~3~, the value of the apparent second order rate constant (k~cat~/K~m~) is close to that expected for a diffusion‐controlled reaction. In H~2~‐production however, the value of k~cat~/K~m~ with cytochrome c~3~ is almost 200 times lower. When methyl viologen is used as mediator, the value of k~cat~/K~m~ is the same in both directions and is intermediate to the values obtained with cytochrome c~3~.
The close to optimum value of k~cat~/K~m~ in H~2~‐oxidation with cytochrome c~3~ as electron acceptor is discussed with respect to the biological role of this and related hydrogenases.
H~2~‐production occurred with the hydrogenase in a system where the mediator was reduced with either of three photosensitizers (proflavin, 5‐deazariboflavin, Zn‐tetraphenyl porphyrin sulphonate) upon illumination. The efficiency of different mediators is discussed.