The ferredoxin/thioredoxin system:  a key element in the regulatory function of light in photosynthesis.
In addition to its well-established function in supplying the energy for carbon dioxide assimilation, light plays a regulatory role in photosynthesis.  The ferredoxin/thioredoxin system is a major mechanism whereby light functions in this capacity.  Here, light absorbed by chlorophyll is converted via ferredoxin into a reductant messenger, reduced thioredoxin, that interacts with key target enzymes, thereby changing their catalytic activities.  In this way, the green plant achieves maximum efficiency of its photosynthetic (light) and heterotrophic (dark) capabilities.
Buchanan
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Division of Molecular Plant Biology, University of California, Berkeley 94720, USA.
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002736:Chloroplasts / Q000201:enzymology*; D004229:Dithiothreitol / Q000737:chemistry; D004789:Enzyme Activation; D005288:Ferredoxins / Q000378:metabolism*; D007506:Iron-Sulfur Proteins; D008027:Light; D008291:Malate Dehydrogenase; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D010944:Plants / Q000201:enzymology; D013879:Thioredoxins / Q000378:metabolism*
D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D013879:Thioredoxins; D009249:NADP; D000255:Adenosine Triphosphate; D010088:Oxidoreductases; D008291:Malate Dehydrogenase; C021588:ferredoxin-thioredoxin reductase; D004229:Dithiothreitol