Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phototrophic organisms use photosynthesis to convert solar energy into chemical energy. In nature, the chemical energy is stored in a diverse range of biopolymers. These sunlight-derived, energy-rich biopolymers can be converted into environmentally clean and CO(2) neutral fuels. A select group of photosynthetic microorganisms have developed the ability to extract and divert protons and electrons derived from water to chloroplast hydrogenase(s) to produce molecular H(2) fuel. Here, we describe the development and characterization of C. reinhardtii strains, derived from the high H(2) production mutant Stm6, into which the HUP1 (hexose uptake protein) hexose symporter from Chlorella kessleri was introduced. The isolated cell lines can use externally supplied glucose for heterotrophic growth in the dark. More importantly, external glucose supply (1mM) was shown to increase the H(2) production capacity in strain Stm6Glc4 to approximately 150% of that of the high-H(2) producing strain, Stm6. This establishes the foundations for a new fuel production process in which H(2)O and glucose can simultaneously be used for H(2) production. It also opens new perspectives on future strategies for improving bio-H(2) production efficiency under natural day/night regimes and for using sugar waste material for energy production in green algae as photosynthetic catalysts.
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PMID:Functional integration of the HUP1 hexose symporter gene into the genome of C. reinhardtii: Impacts on biological H(2) production. 1762 61

Moorella thermoacetica ferments glucose to three acetic acids. In the oxidative part of the fermentation, the hexose is converted to 2 acetic acids and 2 CO(2) molecules with the formation of 2 NADH and 2 reduced ferredoxin (Fd(red)(2-)) molecules. In the reductive part, 2 CO(2) molecules are reduced to acetic acid, consuming the 8 reducing equivalents generated in the oxidative part. An open question is how the two parts are electronically connected, since two of the four oxidoreductases involved in acetogenesis from CO(2) are NADP specific rather than NAD specific. We report here that the 2 NADPH molecules required for CO(2) reduction to acetic acid are generated by the reduction of 2 NADP(+) molecules with 1 NADH and 1 Fd(red)(2-) catalyzed by the electron-bifurcating NADH-dependent reduced ferredoxin:NADP(+) oxidoreductase (NfnAB). The cytoplasmic iron-sulfur flavoprotein was heterologously produced in Escherichia coli, purified, and characterized. The purified enzyme was composed of 30-kDa (NfnA) and 50-kDa (NfnB) subunits in a 1-to-1 stoichiometry. NfnA harbors a [2Fe2S] cluster and flavin adenine dinucleotide (FAD), and NfnB harbors two [4Fe4S] clusters and FAD. M. thermoacetica contains a second electron-bifurcating enzyme. Cell extracts catalyzed the coupled reduction of NAD(+) and Fd with 2 H(2) molecules. The specific activity of this cytoplasmic enzyme was 3-fold higher in H(2)-CO(2)-grown cells than in glucose-grown cells. The function of this electron-bifurcating hydrogenase is not yet clear, since H(2)-CO(2)-grown cells additionally contain high specific activities of an NADP(+)-dependent hydrogenase that catalyzes the reduction of NADP(+) with H(2). This activity is hardly detectable in glucose-grown cells.
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PMID:Electron bifurcation involved in the energy metabolism of the acetogenic bacterium Moorella thermoacetica growing on glucose or H2 plus CO2. 2258 75