Inhibitor studies on non-photochemical plastoquinone reduction and H(2) photoproduction in Chlamydomonas reinhardtii.

Abstract

In the absence of PSII, non-photochemical reduction of plastoquinones (PQs) occurs following NADH or NADPH addition in thylakoid membranes of the green alga Chlamydomonas reinhardtii. The nature of the enzyme involved in this reaction has been investigated in vitro by measuring chlorophyll fluorescence increase in anoxia and light-dependent O(2) uptake in the presence of methyl viologen. Based on the insensitivity of these reactions to rotenone, a type-I NADH dehydrogenase (NDH-1) inhibitor, and their sensitivity to flavoenzyme inhibitors and thiol blocking agents, we conclude to the involvement of a type-II NADH dehydrogenase (NDH-2) in PQ reduction. Intact Chlamydomonas cells placed in anoxia have the property to produce H(2) in the light by a Fe-hydrogenase which uses reduced ferredoxin as an electron donor. H(2) production also occurs in the absence of PSII thanks to the existence of a non-photochemical pathway of PQ reduction. From inhibitors effects, we suggest the involvement of a plastidial NDH-2 in PSII-independent H(2) production in Chlamydomonas. These results are discussed in relation to the absence of ndh genes in Chlamydomonas plastid genome and to the existence of 7 ORFs homologous to type-II NDHs in its nuclear genome.

• Authors: Florence Mus, Laurent Cournac, Véronique Cardettini, Amandine Caruana, Gilles Peltier
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1708 Issue 3 Pg. 322-32 (Jul 15 2005) ISSN: 0006-3002 [Print] Netherlands
• PMID: 15950924 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Enzyme Inhibitors
• Photosystem II Protein Complex
• Rotenone
• Hydrogen
• NADH dehydrogenase (quinone)
• Quinone Reductases
• NADH Dehydrogenase
• Plastoquinone

Topics

• Animals
• Cell Hypoxia
• Chlamydomonas reinhardtii (drug effects, metabolism)
• Electron Transport
• Enzyme Inhibitors (pharmacology)
• Hydrogen (metabolism)
• NADH Dehydrogenase (antagonists & inhibitors, metabolism)
• Oxidation-Reduction
• Photochemistry
• Photosystem II Protein Complex
• Plastoquinone (metabolism)
• Quinone Reductases (antagonists & inhibitors)
• Rotenone (pharmacology)
• Substrate Specificity
• Thylakoids (metabolism)