Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A particulate preparation (MgP) capable of photosynthetic CO(2) assimilation without the addition of stromal protein was obtained by rupturing whole spinach (Spinacia oleracea var. America) chloroplasts in 15 millimolar MgCl(2) buffered with Tricine at pH 8.5. This CO(2) assimilation was dependent upon light, inorganic phosphate, ferredoxin, ADP, NAD or NADP, and primer. Excepting glycolate, the products of CO(2) fixation by MgP were similar to those found with whole chloroplasts.Glycerate-3-phosphate (PGA), fructose-1, 6-bisphosphate (FBP), and ribose-5-phosphate (R5P) but not fructose-6-P (F6P) functioned as primers. Concentrations of PGA and FBP but not of R5P higher than 2 millimolar were inhibitory to CO(2) fixation. A lag of CO(2) fixation was observed with PGA and FBP but not with R5P. This lag as well as inhibition by NADP, ADP, and ATP in the FBP-primed preparation was eliminated by an equimolar mixture of FBP plus F6P indicating FBPase as the sensitive site. NADP, ADP, and ATP also blocked CO(2) fixation by the PGA-fortified preparation but inhibition was even more sensitive than that observed when FBP was added. Inhibition by AMP in the PGA and FBP-primed preparations was not affected by the addition of F6P. When R5P was the starting primer, inhibition of CO(2) fixation was relatively insensitive to the adenylates and NADP. In contrast to the parent whole chloroplast, CO(2) fixation by MgP was insensitive to high (5 millimolar) inorganic phosphate. Depending upon the ferredoxin concentration, NAD was as effective as NADP in supporting CO(2) fixation.
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PMID:Characterization of a Photosynthesizing Reconstituted Spinach Chloroplast Preparation : REGULATION BY PRIMER, ADENYLATES, FERREDOXIN, AND PYRIDINE NUCLEOTIDES. 1666 54

The light activation of fructose-1,6-bisphosphatase (EC 3.1.3.11) and sedoheptulose-1,7-bisphosphatase (EC 3.1.3.37) was inhibited in isolated intact spinach (Spinacia oleracea L.) chloroplasts exposed to reduced osmotic potentials. Decreases in the velocity and magnitude of light activation correlated with the overall reduction in CO2 fixation rates. Responses of osmotically stressed chloroplasts to both varying pH and exogeous dihydroxyacetone phosphate (DHAP) or 3-phosphoglycerete (PGA) were examined. In the presence of DHAP, the absolute rate of CO2 fixation was increased and this increase was most pronounced at alkaline pH. Enhanced light activation of these enzymes was also observed under these conditions. However, in the presence of PGA, similar increases in photosynthetic rate and enzyme activation were not evident. Light-dependent stromal alkalization was unaffected by the stress treatments. Inhibition of light activation under hypertonic conditions is discussed in terms of substrate availability, possible alterations of the redox state of ferredoxin and associated electron carriers, and inhibited enzyme-enzyme or enzyme-substrate interactions involved in the light activation process.
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PMID:Inhibited light activation of fructose and sedoheptulose bisphosphatase in spinach chloroplasts exposed to osmotic stress. 2425 69