Studies on the regulatory properties of chloroplast fructose-1,6-bisphosphatase.
The regulatory properties of chloroplast fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, (EC 3.1.3.11) were examined with a homogeneous enzyme preparation isolated from spinach leaves. The activation of the enzyme, that was earlier shown to occur via reduced thioredoxin, was found to be accompanied by a structural change that took place more slowly than the rate of catalysis. The recently found deactivation of the thioredoxin-activated enzyme by physiological oxidants such as oxidized glutathione and dehydroascorbic acid was also slow relative to catalysis. Under the conditions used, the activated enzyme showed a pH optimum of about 8.0, whereas the corresponding value for the non-activated form was pH 8.8. The importance of the thioredoxin-linked mechanism of enzyme regulation that is effected through photoreduced ferredoxin and ferredoxin-thioredoxin reductase is discussed in relation to other light-controlled regulatory agents in chloroplasts.
D002736:Chloroplasts / Q000201:enzymology*; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010084:Oxidation-Reduction; D010944:Plants; D013879:Thioredoxins / Q000494:pharmacology
D013879:Thioredoxins; D006597:Fructose-Bisphosphatase; D008274:Magnesium; D004229:Dithiothreitol