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PubMed1993

Effect of glpT and glpD mutations on expression of the phoA gene in Escherichia coli.

In vivo 31P nuclear magnetic resonance analysis of Escherichia coli cells showed that the intracellular concentration of P(i) remained constant in wild-type and in a glpT mutant strain whether the cells were grown on excess (2 mM) P(i) or sn-glycerol-3-phosphate as a phosphate source. The function of the phoA promoter (measured by beta-galactosidase activity in a phoA-lacZ fusion strain) was repressed when glpT+ cells were utilizing sn-glycerol-3-phosphate as the sole source of phosphate. These cells were devoid of alkaline phosphatase activity. However, the phoA promoter was fully active in a glpT mutant. These results indicated that the repression of the enzyme synthesis was not due to a variation in the level of cytoplasmic P(i) but was due to the P(i) excreted into the periplasm and/or to the medium.

Alkaline Phosphatase↗
PubMed1994

The pho regulon-dependent Ugp uptake system for glycerol-3-phosphate in Escherichia coli is trans inhibited by Pi.

sn-Glycerol-3-phosphate (G3P) or glyceryl phosphoryl phosphodiesters, the substrates of the phoB-dependent Ugp transport system, when transported exclusively through this system, can serve as a sole source of phosphate but not as a sole source of carbon (H. Schweizer, M. Argast, and W. Boos, J. Bacteriol. 150:1154-1163, 1982). In order to explain this phenomenon, we tested two possibilities: repression of the pho regulon by Ugp-mediated transport and feedback inhibition by internal G3P or its degradation product Pi. Using an ugp-lacZ fusion, we found that the expression of ugp does not decline upon exposure to G3P, in contrast to the repressing effect of transport of Pi via the Pst system. This indicated that the Ugp system becomes inhibited after the uptake and metabolism of G3P. Using 32P-labeled G3P, we observed that little Pi is released by cells taking up G3P via the Ugp system but large amounts of Pi are released when the cells are taking up G3P via the GlpT system. Using a glpD mutant that could not oxidize G3P but which could still phosphorylate exogenous glycerol to G3P after GlpF-mediated transport of glycerol, we could not find trans inhibition of Ugp-mediated uptake of exogenous 14C-G3P. However, when allowing uptake of Pi via Pst, we observed a time-dependent inhibition of 14C-G3P taken up by the Ugp transport system. Inhibition was half maximal after 2 min and could be elicited by Pi concentrations below 0.5 mM. Cells had to be starved for Pi in order to observe this inhibition. We conclude that the activity of the Ugp transport system is controlled by the level of internal phosphate.

Bacterial Proteins↗
PubMed1963

BIOSYNTHESIS OF SERINE IN ESCHERICHIA COLI AND SALMONELLA TYPHIMURIUM.

Umbarger, H. E. (Long Island Biological Association, Cold Spring Harbor, N.Y.), Merle A. Umbarger, and Patrick M. L. Siu. Biosynthesis of serine in Escherichia coli and Salmonella typhimurium. J. Bacteriol. 85:1431-1439. 1963.-Evidence for the operation in extracts of Escherichia coli of a pathway from glucose to serine involving 3-phosphoglycerate, phosphohydroxypyruvate, and phosphoserine as intermediates was obtained by the technique of isotopic competition. The steps of the pathway were demonstrated in extracts of E. coli and Salmonella typhimurium. The first reaction was studied in the reverse of the biosynthetic direction by observing the disappearance of reduced nicotinamide adenine dinucleotide in the presence of phosphohydroxypyruvate. The enzyme catalyzing this reaction was missing in two E. coli mutants that required serine or glycine for growth and in a representative of one of two genetically distinct classes of S. typhimurium serine-glycine auxotrophs. The second reaction, the amination of phosphohydroxypyruvate, was also studied in the reverse of the biosynthetic direction using alpha-ketoglutarate as the amino acceptor in a transamination reaction with phosphoserine. The final step, the cleavage of phosphoserine, could not be catalyzed by extracts prepared from cells of S. typhimurium serine-glycine auxotrophs of the second genetic class. It has been concluded that these three reactions provide the only significant pathway to serine in these organisms.

Alanine↗
PubMed1963

ENZYME SYSTEMS IN THE MYCOBACTERIA. XV. INITIAL STEPS IN THE METABOLISM OF GLYCEROL.

Goldman, Dexter S. (Veterans Administration Hospital, Madison, Wis.). Enzyme systems in the mycobacteria. XV. Initial steps in the metabolism of glycerol. J. Bacteriol. 86:30-37. 1963.-In cell-free extracts of strain H37Ra of Mycobacterium tuberculosis, glycerol is metabolized first by oxidation to dihydroxyacetone. A kinase was partially purified and shown to phosphorylate dihydroxyacetone; in the presence of the glyceraldehyde-3-phosphate dehydrogenase system, the product of the kinase reaction was further oxidized to 3-phosphoglycerate. The role of alpha-glycerol phosphate in the metabolism of strain H37Ra is discussed.

Glyceric Acids↗
PubMed1964

GLYOXYLATE FERMENTATION BY STREPTOCOCCUS ALLANTOICUS.

Valentine, R. C. (University of Illinois, Urbana), H. Drucker, and R. S. Wolfe. Glyoxylate fermentation by Streptococcus allantoicus. J. Bacteriol. 87:241-246. 1964.-Extracts of Streptococcus allantoicus were found to degrade glyoxylate, yielding tartronic semialdehyde and CO(2). Tartronic semialdehyde was prepared chemically, and its properties were compared with the enzymatic product: reduction by sodium borohydride yielded glycerate; heating at 100 C yielded glycolaldehyde and CO(2); autoxidation yielded mesoxalic semialdehyde; periodate oxidation yielded glyoxylate and a compound presumed to be formate. Tartronic semialdehyde reductase was present in extracts of S. allantoicus and in a species of Pseudomonas grown on allantoin. A scheme for the synthesis of acetate from glyoxylate by S. allantoicus is discussed.

Acetates↗
PubMed1969

Two forms of D-glycerate kinase in Escherichia coli.

Escherichia coli K-12 synthesizes two chromatographically distinct forms of glycerate kinase which differ both in their thermolability and in the dependence of their activity upon pH. One enzymatic form, GK I, is found in cells grown with glycerate, glucarate, or glycolate. Of these compounds, glycolate is the only carbon source that elicits the synthesis of the second enzymatic form, GK II.

Chromatography↗
PubMed2006

Molecular dynamics simulation of interactions in glycolytic enzymes.

Two glycolytic enzymes, phosphoglycerate mutase (PGM) and enolase from Saccharomyces cerevisiae, have been chosen to detect complex formation and possible channeling, using molecular dynamics simulation. The enzymes were separated by 10 angstroms distance and placed in a water-filled box of size 173 x 173 x 173 angstroms. Three different orientations have been investigated. The two initial 3-phosphoglycerate substrate molecules near the active centers of the initial structure of PGM have been replaced with final product (2-phosphoglycerate) molecules, and 150 mM NaCl together with three Mg2+ ions have been added to the system to observe post-catalytic activity under near-physiological conditions. Analysis of interaction energies and conformation changes for 3 nsec simulation indicates that PGM and enolase do show binding affinity between their near active regions, which is necessary for channeling to occur. Interaction of the C-terminal residues Ala239 and Val240 of PGM (which partially "cap" the 2-phosphoglycerate) with enolase also favors the existence of channeling.

Binding Sites↗
PubMed1981

2-phosphoglycerate phosphatase and serine biosynthesis in Veillonella alcalescens.

The constituent enzymes for the phosphorylated and nonphosphorylated serine biosynthetic pathways in Veillonella alcalescens were identified and included phosphoserine phosphatase, 3-phosphoglycerate dehydrogenase, glycerate dehydrogenase, phosphoserine aminotransferase, and serine-pyruvate aminotransferase. Cell extracts of the organism were also found to cause the specific dephosphorylation of 2-phosphoglycerate. The phosphatase was purified 39-fold by manganese chloride precipitation, ammonium sulfate precipitation, and DEAE-cellulose chromatography. Sephadex G-200 gel filtration data established an apparent molecular weight of 50000 for the enzyme. The 2-phosphoglycerate phosphatase had a pH optimum of 5.5 and was distinct from phosphoglyceromutase. Assays conducted with the purified enzyme on a number of other phosphorylated intermediates indicated that the phosphatase was most specific for 2-phosphoglycerate. Glucerate, hydroxypyruvate, and serine inhibited the enzyme, whereas succinate stimulated activity. Veillonella 2-phosphoglycerate phosphatase is the first such enzyme to be described in a prokaryote and is probably involved in glycerate generation for the nonphosphorylated serine biosynthetic pathway.

Chromatography, DEAE-Cellulose↗
PubMed2006

Effects of 3-phosphoglycerate and other metabolites on the activation of AMP-activated protein kinase by LKB1-STRAD-MO25.

Skeletal muscle contraction results in the phosphorylation and activation of the AMP-activated protein kinase (AMPK) by an upstream kinase (AMPKK). The LKB1-STE-related adaptor (STRAD)-mouse protein 25 (MO25) complex is the major AMPKK in skeletal muscle; however, LKB1-STRAD-MO25 activity is not increased by muscle contraction. This relationship suggests that phosphorylation of AMPK by LKB1-STRAD-MO25 during skeletal muscle contraction may be regulated by allosteric mechanisms. In this study, we tested an array of metabolites including, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, 3-phosphoglycerate (3-PG), glucose 1-phosphate, glucose 1,6-bisphosphate, ADP, carnitine, acetylcarnitine, IMP, inosine, and ammonia for allosteric regulation. ADP inhibited both AMPK and LKB1-STRAD-MO25 actions, but probably is not important physiologically because of the low free ADP inside the muscle fiber. We found that 3-PG stimulated LKB1-STRAD-MO25 activity and allowed for increased AMPK phosphorylation. 3-PG did not stimulate LKB1-STRAD-MO25 activity toward the peptide substrate LKB1tide. These results have identified 3-PG as an AMPK-specific regulator of AMPK phosphorylation and activation by LKB1-STRAD-MO25.

AMP-Activated Protein Kinase Kinases↗
PubMed1984

Erythrocyte phosphates and hemoglobin function in monotremes and some marsupials.

Hematologic values, red blood cell (RBC) organic phosphate composition, hemoglobin function, and hemoglobin composition have been determined on blood from the monotremes, the duckbill platypus and the echidna, and three species of marsupials, the Tasmanian devil, the wallaby, and the brush-tail possum. Blood from the platypus had a RBC count of 8.63 X 10(6)/mm3, a mean corpuscular volume of 49.1 millemicron3, and a white blood cell count of 26.0 X 10(3)/mm3. The RBCs from the monotremes and the three marsupials exhibited hemoglobin polymorphism, each with three hemoglobin components. Addition of ATP, 2,3-bisphosphoglycerate (2,3-P2-glycerate), or inositol pentakisphosphate (inositol-P5) to phosphate-free hemoglobin from each species decreased hemoglobin oxygen affinity; the order of effect of these compounds was ATP less than 2,3-P2-glycerate less than inositol-P5. The RBCs of all species had concentrations of 2,3-P2-glycerate ranging from 6.02 mumol/ml RBCs in the wallaby to 10.39 mumol/ml RBCs in the possum. The RBCs from the three species of marsupials had concentrations of ATP ranging from 0.24 mumol/ml RBCs in the possum to 0.80 mumol/ml RBCs in the Tasmanian devil. The level of ATP in RBCs of the platypus and echidna were 0.06 and 0.03 mumol/ml RBCs, respectively.

Adenosine Triphosphate↗