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)

Ribulose-diphosphate carboxylase from Thiobacillus novellus has been purified to hemogeneity as observed by polyacrylamide gel electrophoresis and U.V. light observation during sedimentation velocity analysis. The optimum pH for the enzyme with Tris-HCl buffers was about 8.2. Concentrations of this buffer in excess of 80 mM were inhibitory. The apparent Km for RuDP was about 14.8 muM with a Hill value of 1.5, for HCO3- the apparent Km was about 11.7 mM with an n value of 1.18 and for Mg2+ about 0.61 mM. The enzyme was specific for this cation. Relatively high concentrations of either Hg2+ or pCMB were required before significant inhibition was observed. Activity declined slowly during a 4-hr incubation period in either 3.0 M or 8.0 M urea. Incubation for 12 hrs resulted in complete loss of activity which was not prevented by 10 mM Mg2+ and was not reversed by dialysis and subsequent addition of 10 mM cysteine. Polyacrylamide gel electrophoresis revealed a loss of the major band and the appearance of 2 new bands. SDS polyacrylamide gel electrophoresis gave an average M.W. of 73500 +/- 2500 for the slower moving band and 12250 +/- 2500 for the faster moving. However, incubation in urea for up to 40 hrs revealed a decrease in the M.W. of the slower moving band to about 60000. The Ea for the enzyme was calculated to be about 18.85 kcal mole-1, with the possibility of a "break" between 40 and 50 degrees C. The Q10 was 3.07 between 20 and 30 degrees C whereas between 30 to 40 degrees C it was 3.31. Only phosphorylated compounds caused significant inhibition of enzyme activity. They included ADP, FDP, F6P, G6P, PEP, 6PG, 2-PGA, R1P, R5P, and Ru5p.
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PMID:Properties and regulation of ribulose diphosphate carboxylase from Thiobacillus novellus. 24 94

We have studied the effects of 2,3-diphosphoglycerate (2,3-DPG), 3-phosphoglycerate (3-PG), 3-phosphoglyceraldehyde (3-PGA), 2-phosphoglycerate (2-PG) and beta-glycerol phosphate (beta-GP) on platelet aggregation and on thromboxane B2 (TXB2) formation. The results show that 2,3-DPG, 3-PG, and 3-PGA inhibited platelet aggregation and TXB2 formation induced by norepinephrine, ADP, epinephrine, and collagen; but they also induced platelet aggregation and TXB2 formation in the presence of subthreshold concentrations of Na arachidonate. 2-PG and beta-GP were inactive. The results also show that there is a structure-function relationship between 2,3-DPG, 3-PG, and 3-PGA with platelet aggregation phenomena and prostaglandin synthesis.
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PMID:Structure-function relationship of 3-phosphoglycerate analogues with platelet aggregation and thromboxane A2 formation. 359 60

Prostaglandins are analogs of the parent 20 carbon prostanoic acid. They are divided into 4 series: PGE; PGF; PGA; PGB, according to the presence of functionalities in the cyclopentane structure. Biosynthesis of prostaglandins were first independently reported by Bergstrom et.al. and van Dorp et.al. who showed that certain w-6-unsaturated fatty acids were biological precursors of prostaglandins. Later, various investigators reported the biosynthesis of prostaglandins of the different series. The 2 most widely used routes of prostaglandins synthesis are 1) the Corey cyclopentyl-lactone route, and 2) the bicyclohexane route. The synthesis is divided into 1) naturally occuring primary prostaglandins and 2) the prostaglandin analogs and derived prostaglandins. Because of the general instability of natural prostaglandins in the basic and acidic milieu, various preparations of prostaglandins and chemically stable dosage forms have been developed. Various methods used in analyzing prostaglandins include: 1) TLC; 2) GLC; 3) spectral methods; 4) radioimmunoassay; and 5) enzymatic assay. In vitro and in vivo studies on the metabolism and catabolism of various prostaglandins showed that they are rapidly metabolized in various animal systems and humans. The major routes for this metabolic transformation are: 1) oxidation of the secondary C15 hydroxy group; 2) reduction of the C13 double bond; 3) B-oxidation; 4) w-hydroxylation; and 5) w-oxidation. Prostaglandins produce a wide range of biological effects on animal and human systems (the reproductive; gastrointestinal; respiratory; and cardiovascular systems). The biological actions of prostaglandins on animal and human reproductive tissue vary depending on the particular prostaglandin studied and hormonal state of the tissue. Certain prostaglandins can decrease the tonus, frequency, and amplitude of spontaneous contractions of human uterine strips while other prostaglandins can cause contraction of isolated myometrial strips. Prostaglandins are widely used in labor induction; induction of therapeutic abortion; and fertility control. Prostaglandins have also been found to either increase or decrease cyclic AMP; inhibit ADP-induced platelet aggregation; lower blood pressure in animals; affect lipid and carbohydrate metabolism, and prevent adjuvant arthritis.
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PMID:Prostaglandins. 456 72

This paper describes a simple and rapid method for the purification of glucose-6-phosphate dehydrogenase from bovine lens, together with analysis of the kinetic behaviour and some properties of the enzyme. The purification consisted of two steps, 2',5'-ADP-Sepharose 4B affinity chromatography and DEAE Sepharose Fast Flow ion exchange chromatography in procedure which took two working days. The enzyme was obtained with a yield of 13.7% and had a specific activity of 2.64 U/mg protein. The overall purification was about 19,700-fold. The molecular weight of the enzyme was found to be 62 +/- 3 kDa by Sephadex G-200 gel filtration chromatography. A protein band corresponding to a molecular weight of 69.2 +/- 3.2 kDa was obtained on SDS polyacrylamide slab gel electrophoresis. On chromatofocusing, lens glucose-6-phosphate dehydrogenase gave a single peak at pI 5.14. The activation energy of the reaction catalyzed by the enzyme was calculated from Arrhenius plot as Ea = 5.88 kcal/mol. The pH versus velocity curve had two peaks at pH 7.7 and 9.6. By the double-reciprocal plots and the product inhibition studies, it was shown that the enzyme follows 'Ordered Bi Bi' sequential kinetics. From the graphical and statistical analyses, KmNADP+, KmG-6-P, KiNADPH, Ki6-PGA were estimated to be 0.008 +/- 0.002, 0.035 +/- 0.013, 0.173 +/- 0.007 and 1.771 +/- 0.160 mM, respectively. The observed kinetic behaviour of glucose-6-phosphate dehydrogenase from bovine lens was in accordance with the enzyme from other sources.
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PMID:A rapid method for the purification of glucose-6-phosphate dehydrogenase from bovine lens. 1046 35

Anticoagulative effect of pepsin is observed in vitro when its concentration is 36 microM and higher. This effect is due to inhibition of fibrin monomer polymerization. Protamine abolishes anticoagulative effect of pepsin. Pepsin does not influence platelet aggregation induced by ADP and collagen.
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PMID:Anticoagulative effect of pepsin. 1069 79

Cytosolic pyruvate kinase (ATP: Pyruvate phosphotransferase, EC 2.7.1.40; PKc) was purified to apparent homogeneity with about 22% recovery from developing seeds of Brassica campestris using (NH4)2SO4 fractionation, DEAE-cellulose chromatography, gel filtration through Sepharose-CL-6B and affinity chromatography through reactive Blue Sepharose-CL-6B. The purified enzyme with molecular mass of about 214 kDa was a heterotetramer with subunit molecular mass of 55 and 57 kDa. The enzyme showed maximum activity at pH 6.8 and absolute requirement for a divalent (Mg2+) and a monovalent (K+) cation for activity. Typical Michaelis-Menten kinetics was obtained for both the substrates with Km values of 0.10 and 0.11 mM for PEP and ADP, respectively. The enzyme could also use UDP or GDP as alternative nucleotides, but with lower Vmax and lesser affinities. The enzyme was inhibited by glutamate, glutamine, fumarate, citrate, isocitrate, oxalate, 2-PGA, ATP, UTP and GTP and activated by glucose-6-phosphate, fructose-1,6-bisphosphate and Pi, suggesting its regulation mainly by TCA cycle intermediates and the cellular need for carbon skeletons for amino acid biosynthesis. ATP inhibition was of competitive type with respect to PEP and non-competitive with respect to ADP. Similarly, oxalate inhibition was also of competitive type with respect to PEP and non-competitive with respect to ADP. Initial velocity and product inhibition studies except for pyruvate inhibition were consistent for a compulsory-ordered tri-bi mechanism.
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PMID:Purification and characterization of cytosolic pyruvate kinase from developing seeds of Brassica campestris L. 1098 13

Photosynthetic carbon metabolism was investigated in antisense Arabidopsis lines with decreased expression of sucrose phosphate synthase (SPS) and cytosolic fructose-1,6-bisphosphatase (cFBPase). In the light, triose phosphates are exported from the chloroplast and converted to sucrose via cFBPase and SPS. At night, starch is degraded to glucose, exported and converted to sucrose via SPS. cFBPase therefore lies upstream and SPS downstream of the point at which the pathways for sucrose synthesis in the day and night converge. Decreased cFBPase expression led to inhibition of sucrose synthesis; accumulation of phosphorylated intermediates; Pi-limitation of photosynthesis; and stimulation of starch synthesis. The starch was degraded to maintain higher levels of sugars and a higher rate of sucrose export during the night. This resembles the response in other species when expression of enzymes in the upper part of the sucrose biosynthesis pathway is reduced. Decreased expression of SPS inhibited sucrose synthesis, but phosphorylated intermediates did not accumulate and carbon partitioning was not redirected towards starch. Sugar levels and sucrose export was decreased during the night as well as during the day. Although ribulose-1,5-bisphosphate regeneration and photosynthesis were inhibited, the PGA/triose-P ratio remained low and the ATP/ADP ratio high, showing that photosynthesis was not limited by the rate at which Pi was recycled during end-product synthesis. Two novel responses counteracted the decrease in SPS expression and explain why phosphorylated intermediates did not accumulate, and why allocation was not altered in the antisense SPS lines. Firstly, a threefold decrease of PPi and a shift of the UDP-glucose/hexose phosphate ratio favoured sucrose synthesis and prevented the accumulation of phosphorylated intermediates. Secondly, there was no increase of AGPase activity relative to cFBPase activity, which would prevent a shift in carbon allocation towards starch synthesis. These responses are presumably triggered when sucrose synthesis is decreased in the night, as well as by day.
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PMID:Decreased expression of two key enzymes in the sucrose biosynthesis pathway, cytosolic fructose-1,6-bisphosphatase and sucrose phosphate synthase, has remarkably different consequences for photosynthetic carbon metabolism in transgenic Arabidopsis thaliana. 1099 87

The allosteric enzyme ADP-Glc pyrophosphorylase (AGPase) catalyzes the synthesis of ADP-Glc, a rate-limiting step in starch synthesis. Plant AGPases are heterotetramers, most of which are activated by 3-phosphoglyceric acid (3-PGA) and inhibited by phosphate. The objectives of these studies were to test a hypothesis concerning the relative roles of the two subunits and to identify regions in the subunits important in allosteric regulation. We exploited an Escherichia coli expression system and mosaic AGPases composed of potato (Solanum tuberosum) tuber and maize (Zea mays) endosperm subunit fragments to pursue this objective. Whereas potato and maize subunits have long been separated by speciation and evolution, they are sufficiently similar to form active mosaic enzymes. Potato tuber and maize endosperm AGPases exhibit radically different allosteric properties. Hence, comparing the kinetic properties of the mosaics to those of the maize endosperm and potato tuber AGPases has enabled us to identify regions important in regulation. The data herein conclusively show that both subunits are involved in the allosteric regulation of AGPase. Alterations in the small subunit condition drastically different allosteric properties. In addition, extent of 3-PGA activation and extent of 3-PGA affinity were found to be separate entities, mapping to different regions in both subunits.
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PMID:Both subunits of ADP-glucose pyrophosphorylase are regulatory. 1512 37

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

(14)CO(2) photoassimilation in the presence of MgATP, MgADP, and MgAMP was investigated using intact chloroplasts from Sedum praealtum, a Crassulacean acid metabolism plant, and two C(3) plants: spinach and peas. Inasmuch as free ATP, ADP, AMP, and uncomplexed Mg(2+) were present in the assays, their influence upon CO(2) assimilation was also examined. Free Mg(2+) was inhibitory with all chloroplasts, as were ADP and AMP in chloroplasts from Sedum and peas. With Sedum chloroplasts in the presence of ADP, the time course of assimilation was linear. However, with pea chloroplasts, ADP inhibition became progressively more severe, resulting in a curved time course. ATP stimulated assimilation only in pea chloroplasts. MgATP and MgADP stimulated assimilation in all chloroplasts. ADP inhibition of CO(2) assimilation was maximal at optimum orthophosphate concentrations in Sedum chloroplasts, while MgATP stimulation was maximal at optimum or below optimum concentrations of orthophosphate. MgATP stimulation in peas and Sedum and ADP inhibition in Sedum were not sensitive to the addition of glycerate 3-phosphate (PGA).PGA-supported O(2) evolution by pea chloroplasts was not inhibited immediately by ADP; the rate of O(2) evolution slowed as time passed, corresponding to the effect of ADP on CO(2) assimilation, and indicating that glycerate 3-phosphate kinase was a site of inhibition. Likewise, upon the addition of AMP, inhibition of PGA-dependent O(2) evolution became more severe with time. This did not mirror CO(2) assimilation, which was inhibited immediately by AMP. In Sedum chloroplasts, PGA-dependent O(2) evolution was not inhibited by ADP and AMP. In chloroplasts from peas and Sedum, the magnitude of MgADP and MgATP stimulation of PGA-dependent O(2) evolution was not much larger than that given by ATP, and it was much smaller than MgATP stimulation of CO(2) assimilation. Analysis of stromal metabolite levels by anion exchange chromatography indicated that ribulose 1,5-bisphosphate carboxylase was inhibited by ADP and stimulated by MgADP in Sedum chloroplasts.The appearance of label in the medium was measured when [U-(14)C] ADP-loaded Sedum chloroplasts were challenged with ATP, ADP, or AMP and their Mg(2+) complexes. The rate of back exchange was stimulated by the presence of Mg(2+). This suggests that ATP, ADP, and AMP penetrate the chloroplast slower than their Mg(2+) complexes. A portion of the CO(2) assimilation and O(2) evolution data could be explained by differential penetration rates, and other proposals were made to explain the remainder of the observations.
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PMID:Influence of adenosine phosphates and magnesium on photosynthesis in chloroplasts from peas, sedum, and spinach. 1666 88


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