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At least 217 records · Page 12Linked to original sources
PubMed1984

2,3-Bisphosphoglycerate inhibits the transport of phosphoenolpyruvate across the erythrocyte membrane.

Mono- and bisphosphoglycerate competitively inhibited the transport of phosphoenolpyruvate across the erythrocyte membrane, although phosphoglycerates were impermeable to the cell membrane. The Ki values of 2-phosphoglycerate, 3-phosphoglycerate and 2,3-bisphosphoglycerate were 8.8 mM, 10.4 mM and 4.3 mM, respectively, whereas glucose 6-phosphate had almost no effect on the transport of phosphoenolpyruvate.

2,3-Diphosphoglycerate↗
PubMed1988

Comparative effects of two sulfhydryl reagents on the activities of a multifunctional red cell enzyme: bisphosphoglycerate mutase.

The effects of two sulfhydryl reagents on the three activities of bisphosphoglycerate mutase have been compared. Under N-ethylmaleimide treatment all the activities were inhibited except for 60% of the non-stimulated phosphatase. With iodoacetamide the mutase and the stimulated-phosphatase activities were completely inhibited whereas the non-stimulated phosphatase and 60% of the synthase activities were unaffected. 2,3-bisphosphoglycerate protected all the activities of the enzyme against inactivation by the two sulfhydryl reagents whereas 3-phosphoglycerate protected them only against iodoacetamide. 2-phosphoglycolate had an identical effect to that of 3-phosphoglycerate except for its effect on the non-stimulated phosphatase activity, which was slightly enhanced under N-ethylmaleimide treatment.

2,3-Diphosphoglycerate↗
PubMed2005

Substrate-assisted movement of the catalytic Lys 215 during domain closure: site-directed mutagenesis studies of human 3-phosphoglycerate kinase.

3-Phosphoglycerate kinase (PGK) is a two-domain hinge-bending enzyme. It is still unclear how the geometry of the active site is formed during domain closure and how the catalytic residues are brought into the optimal position for the reaction. Comparison of the three-dimensional structures in various open and closed conformations suggests a large (10 A) movement of Lys 215 during domain closure. This change would be required for direct participation of this side chain in both the catalyzed phospho transfer and the special anion-caused activation. To test the multiple roles of Lys 215, two mutants (K215A and K215R) were constructed from human PGK and characterized in enzyme kinetic and substrate binding studies. For comparison, mutants (R38A and R38K) of the known essential residue, Arg 38, were also produced. Drastic decreases (1500- and 500-fold, respectively), as in the case of R38A, were observed in the kcat values of mutants K215A and K215R, approving the essential catalytic role of Lys 215. In contrast, the R38K mutation caused an only 1.5-fold decrease in activity. This emphasizes the importance of a very precise positioning of Lys 215 in the active site, in addition to its positive charge. The side chain of Lys 215 is also responsible for the substrate and anion-dependent activation, since these properties are abolished upon mutation. Among the kinetic constants mainly the Km values of MgATP and 1,3-BPG are increased (approximately 20- and approximately 8-fold, respectively) in the case of the neutral K215A mutant, evidence of the interaction of Lys 215 with the transferring phospho group in the functioning complex. Weakening of MgATP binding (a moderate increase in Kd), but not of MgADP binding, upon mutation indicates an initial weak interaction of Lys 215 with the gamma-phosphate already in the nonfunctioning open conformation. Thus, during domain closure, Lys 215 possibly moves together with the transferring phosphate; meanwhile, this group is being positioned properly for catalysis.

Adenosine Triphosphate↗
PubMed1994

Antagonistic binding of substrates to 3-phosphoglycerate kinase monitored by the fluorescent analogue 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate.

The analogue of ATP, 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate (TNP-ATP), binds tightly to pig muscle 3-phosphoglycerate kinase. A dissociation constant Kd of 0.0095 +/- 0.0015 mM was determined by fluorimetric titration on the basis of 1:1 stoichiometry. TNP-ATP is a strong competitive inhibitor towards MgATP and MgADP with a Ki of 0.008 +/- 0.001 mM for both substrates. It is also a mixed-type inhibitor towards 3-phosphoglycerate with similar inhibition constants. Binding of TNP-ATP to 3-phosphoglycerate kinase is accompanied by a tenfold intensity increase and a blue shift of about 20 nm in its fluorescence emission spectrum and a shift of the pK of its trinitrophenyl group towards a more acidic pH. These findings suggest that the negatively charged trinitrophenyl group of TNP-ATP significantly contributes to the binding of the analogue. By stepwise replacement of the fluorescent TNP-ATP, the dissociation constants (Kd) for ADP and MgADP binding were determined and found to be 0.78 +/- 0.08 and 0.048 +/- 0.006 mM respectively, which are consistent with the values previously determined by equilibrium dialysis [Molnár and Vas (1993) Biochem J. 293, 595-599]. In similar competitive-titration experiments, ATP and MgATP did not completely substitute for TNP-ATP. For the fraction of the analogue that could be substituted, the dissociation constants for MgATP and ATP were estimated to be 0.27 +/- 0.09 and 0.33 +/- 0.15 mM respectively, close to the values determined by equilibrium dialysis. Using the same method, a significant weakening of binding of both (Mg)ADP and (Mg)ATP could be detected in the presence of 3-phosphoglycerate: their respective Kd values became 0.34 +/- 0.04 and 0.51 +/- 0.22 mM. The reciprocal effect, i.e. weakening of 3-phosphoglycerate binding in the presence of the nucleotide substrates, has been observed previously [Vas and Batke (1984) Eur. J. Biochem. 139, 115-123]. Similarly, a much weaker binding of (Mg)ATP could be observed in the presence of 1,3-bisphosphoglycerate (Kd = 2.30 +/- 0.68 mM). The possible reason for the mutual weakening of substrate binding is discussed in the light of the available structural data.

Adenosine Diphosphate↗
PubMed1992

Phosphoglycerate mutase from Streptomyces coelicolor A3(2): purification and characterization of the enzyme and cloning and sequence analysis of the gene.

The enzyme 3-phosphoglycerate mutase was purified 192-fold from Streptomyces coelicolor, and its N-terminal sequence was determined. The enzyme is tetrameric with a subunit Mr of 29,000. It is 2,3-bisphosphoglycerate dependent and inhibited by vanadate. The gene encoding the enzyme was cloned by using a synthetic oligonucleotide probe designed from the N-terminal peptide sequence, and the complete coding sequence was determined. The deduced amino acid sequence is 64% identical to that of the phosphoglycerate mutase of Saccharomyces cerevisiae and has substantial identity to those of other phosphoglycerate mutases.

2,3-Diphosphoglycerate↗
PubMed1995

Biosynthesis of chylomicron triacylglycerols by rats fed glyceryl or alkyl esters of menhaden oil fatty acids.

We have previously shown great similarity in the distribution of fatty acids in the sn-1 and sn-3 positions of the chylomicron triacylglycerols (TG) from rats fed menhaden oil or its ethyl esters, and have proposed that the acylglycerol products of the phosphatidic acid (PA) pathway (ester feeding) are hydrolyzed to 2-monoacylglycerols (2-MG) prior to reconversion to TG via the 2-MG pathway (oil feeding) and secretion as chylomicrons. As the composition of the sn-2-position would also be retained if the TG were hydrolyzed only to the X-1,2-diacylglycerol (DG) stage before resynthesis, we have now retested the hypothesis by determining the molecular association and reverse isomer content of the sn-1,2- and sn-2,3-DG derived from the chylomicron TG and the PA resulting from the two feedings. The new data demonstrate a better than 90% homology among the molecular species of the PA from the oil and ester feeding, along with the characteristic association of the saturated acids with sn-1- and the unsaturated acids with sn-2-position. Due to increased proportion of unsaturated acids in the sn-1-position of the TG, there was only a 15-20% homology between the PA and the sn-1,2-DG moieties of the chylomicron TG from the oil and ester feeding. A lack of homology was also observed between the PA and free sn-1,2-DG, as well as between the free sn-1,2-DG and the sn-1,2-DG moieties of the chylomicron TG. On the basis of molecular association and the sn-1-/sn-3- reverse isomer content of the chylomicron TG a better than 90% homology was recognized between the chylomicron TG resulting from the oil and ester feeding. It is therefore concluded that hydrolysis to 2-MG followed by reesterification via the 2-MG pathway constitutes the most plausible mechanism for the transfer to chylomicrons of the TG arising from alkyl ester feeding.

Alkylation↗
PubMedDate not supplied

[Dependence of ammonia nitrogen utilization in rabbits on concentration of carbonic acid in tissues].

Under conditions of an increase in the carbonic acid concentration in blood of rabbits (experimental group) utilization of ammonia nitrogen administered to the organism intensifies and simultaneously the level of keto-acids in blood as well as of free amino acids and urea in the liver tissue increases. In these animals as compared to the control ones the content of glutamine in blood and in the liver tissue decreases; the level of alpha-glutarate and glutamate in the liver tissue increases and that of pyruvate lowers. An increase is also observed in reducing power of the liver and kidney cell cytoplasm.

Amino Acids↗
PubMed1978

Binding of substrates and other anions to yeast phosphoglycerate kinase.

1. The binding of all four substrates to yeast phosphoglycerate kinase has been studied using a gel filtration technique. The binding of phosphate and sulphate anions has also been investigated. 2. Two sites for each adenine nucleotide were found, one site being weaker than the other by between 30 and 50-fold. Only one binding site for the phosphoglycerate substrates was found. 3. 1,3-Bisphosphoglycerate (1,3-P2-glycerate) bound to the enzyme approximately 1000 times tighter than the other three substrates, its dissociation constant being 0.06 micrometer at ionic strength 0.15 M. 4. Sulphate and phosphate were mutually competitive and sulphate competed with the binding of all substrates except MgADP. MgADP bound to the enzyme more weakly in the presence of sulphate. The dissociation constant for sulphate binding was 1.6 mM at ionic strength of 0.15 M, and 0.05 mM at ionic strength 0.015 M. 5. These results are consistent with sulphate acting as a competitive inhibitor, as found by kinetic studies at high sulphate concentrations. The activatory effect of sulphate at lower concentrations and the substrate activation phenomea displayed by this enzyme, are interpreted in terms of a two-step dissociation of 1, 3-P2-glycerate. The presence of moderate concentrations of MgATP, 3-phosphoglycerate or sulphate causes acceleration of the rate of dissociation of the product, 1, 3-P2-glycerate, this being the rate-limiting step in the overall enzyme reaction.

Adenosine Diphosphate↗