This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Walker, D. A. Articles by Slabas, A. R. Search for Related Content PubMed PubMed Citation Articles by Walker, D. A. Articles by Slabas, A. R. Agricola Articles by Walker, D. A. Articles by Slabas, A. R.

Articles

Stepwise Generation of the Natural Oxidant in a Reconstituted Chloroplast System ¹

^a Department of Botany, The University, Sheffield S10 2TN, United Kingdom

Isolated chloroplasts which have lost their envelopes and, in consequence, the soluble components which constitute the stroma, will nevertheless evolve O₂ when supplied with an artificial oxidant (the Hill reaction). They will also evolve O₂ with NADP as the Hill oxidant if supplemented with ferredoxin. With catalytic NADP, continuing O₂ evolution can be maintained by the inclusion of a suitable reaction or reaction sequence which reoxidizes NADPH.

In the Benson-Calvin cycle the terminal oxidant is glycerate 1,3-bisphosphate which is generated by phosphorylation of 3-phosphoglycerate, its immediate precursor. Experiments with a reconstituted chloroplast system are described in which this reaction sequence is catalyzed by stromal protein and supported by photophosphorylation of catalytic ADP. In the presence of CO₂, 3-phosphoglycerate can be progressively replaced by ribulose 1,5-bisphosphate, ribose 5-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, and finally by glyceraldehyde 3-phosphate. In this last instance the natural oxidant is regenerated from its own reduction product (via the carboxylation step) and the reaction sequence therefore involves the entire photosynthetic carbon cycle.