scholarly journals Defluorination of 4-fluorothreonine by threonine deaminase

2020 ◽  
Vol 18 (32) ◽  
pp. 6236-6240 ◽  
Author(s):  
Linrui Wu ◽  
Hai Deng
Keyword(s):  
Threonine Deaminase ◽  
E Coli

Threonine deaminase from E. coli catalyses defluorination on 4-fluorothreonine.

scholarly journals Production in Escherichia coli of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) with Differing Monomer Compositions from Unrelated Carbon Sources

2011 ◽  
Vol 77 (14) ◽  
pp. 4886-4893 ◽  
Author(s):  
Quan Chen ◽  
Qian Wang ◽  
Guoqing Wei ◽  
Quanfeng Liang ◽  
Qingsheng Qi
Keyword(s):  
Escherichia Coli ◽  
Control Strategy ◽  
Biosynthetic Pathway ◽  
Feedback Inhibition ◽  
Carbon Sources ◽  
Threonine Deaminase ◽  
Content Type ◽  
E Coli ◽  
Key Factor ◽  
Threonine Biosynthesis

ABSTRACTThe industrial production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has been hindered by high cost and a complex control strategy caused by the addition of propionate. In this study, based on analysis of the PHBV biosynthesis process, we developed a PHBV biosynthetic pathway from a single unrelated carbon source via threonine biosynthesis inEscherichia coli. To accomplish this, we (i) overexpressed threonine deaminase, which is the key factor for providing propionyl-coenzyme A (propionyl-CoA), from different host bacteria, (ii) removed the feedback inhibition of threonine by mutating and overexpressing thethrABCoperon inE. coli, and (iii) knocked out the competitive pathways of catalytic conversion of propionyl-CoA to 3-hydroxyvaleryl-CoA. Finally, we constructed a series of strains and mutants which were able to produce the PHBV copolymer with differing monomer compositions in a modified M9 medium supplemented with 20 g/liter xylose. The largest 3-hydroxyvalerate fraction obtained in the copolymer was 17.5 mol%.

scholarly journals Inhibition of isoleucyl-transfer ribonucleic acid synthetase in Echerichia coli by pseudomonic acid

1978 ◽  
Vol 176 (1) ◽  
pp. 305-318 ◽  
Author(s):  
Julia Hughes ◽  
Graham Mellows
Keyword(s):  
Rna Synthesis ◽  
Inhibitory Effect ◽  
Trna Synthetase ◽  
Threonine Deaminase ◽  
Trna Synthetases ◽  
E Coli ◽  
Naturally Occurring ◽  
Pseudomonic Acid

The mode of action of the antibiotic pseudomonic acid has been studied in Escherichia coli. Pseudomonic acid strongly inhibits protein and RNA synthesis in vivo. The antibiotic had no effect on highly purified DNA-dependent RNA polymerase and showed only a weak inhibitory effect on a poly(U)-directed polyphenylalanine-forming ribosomal preparation. Chloramphenicol reversed inhibition of RNA synthesis in vivo. Pseudomonic acid had little effect on RNA synthesis in a regulatory mutant, E. coli B AS19 RCrel, whereas protein synthesis was strongly inhibited. In pseudomonic acid-treated cells, increased concentrations of ppGpp, pppGpp and ATP were observed, but the GTP pool size decreased, suggesting that inhibition of RNA synthesis is a consequence of the stringent control mechanism imposed by pseudomonic acid-induced deprivation of an amino acid. Of the 20 common amino acids, only isoleucine reversed the inhibitory effect in vivo. The antibiotic was found to be a powerful inhibitor of isoleucyl-tRNA synthetase both in vivo and in vitro. Of seven other tRNA synthetases assayed, only a weak inhibitory effect on phenylalanyl-tRNA synthetase was observed; this presumably accounted for the weak effect on polyphenylalanine formation in a ribosomal preparation. Pseudomonic acid also significantly de-repressed threonine deaminase and transaminase B activity, but not dihydroxyacid dehydratase (isoleucine-biosynthetic enzymes) by decreasing the supply of aminoacylated tRNAIle. Pseudomonic acid is the second naturally occurring inhibitor of bacterial isoleucyl-tRNA synthetase to be discovered, furanomycin being the first.

KINETICS OF THREONINE DEAMINASE OF ESCHERICHIA COLI K-12 AND A STREPTOMYCIN-DEPENDENT MUTANT

1967 ◽  
Vol 45 (1) ◽  
pp. 1-10 ◽  
Author(s):  
I. D. Desai ◽  
W. J. Polglase
Keyword(s):  
Escherichia Coli ◽  
Selective Advantage ◽  
Kinetic Properties ◽  
Wild Type ◽  
Threonine Deaminase ◽  
E Coli ◽  
Type K ◽  
Hyperbolic Curve ◽  
K 12 ◽  
Kinetics Of

The relation between threonine deaminase activity and threonine concentration in sonic extracts of wild-type and streptomycin-dependent Escherichia coli K-12 was found to follow a hyperbolic curve. A similar relationship was obtained between enzyme activity and pyridoxal concentration. However, when serine was used as substrate, the activity–concentration curve was sigmoid, suggesting that serine may be a weaker effector of allosteric transition than threonine. The kinetic properties of the (derepressed) threonine deaminase of streptomycin-dependent E. coli K-12 were found to be similar to those of the enzyme of the wild-type K-12.It is postulated that derepression of threonine deaminase in streptomycin-dependent E. coli K-12 provides a selective advantage which permits exponential growth of this mutant in the presence of L-valine, which is an excretory product of streptomycin-dependent microorganisms.

scholarly journals Homocysteine Toxicity in Escherichia coli Is Caused by a Perturbation of Branched-Chain Amino Acid Biosynthesis

2005 ◽  
Vol 187 (13) ◽  
pp. 4362-4371 ◽  
Author(s):  
Nina L. Tuite ◽  
Katy R. Fraser ◽  
Conor P. O'Byrne
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Biosynthetic Pathway ◽  
Amino Acid Biosynthesis ◽  
Inhibitory Effects ◽  
Acid Biosynthesis ◽  
Threonine Deaminase ◽  
E Coli ◽  
Branched Chain Amino Acid ◽  
Branched Chain

ABSTRACT In Escherichia coli the sulfur-containing amino acid homocysteine (Hcy) is the last intermediate on the methionine biosynthetic pathway. Supplementation of a glucose-based minimal medium with Hcy at concentrations greater than 0.2 mM causes the growth of E. coli Frag1 to be inhibited. Supplementation of Hcy-treated cultures with combinations of branched-chain amino acids containing isoleucine or with isoleucine alone reversed the inhibitory effects of Hcy on growth. The last intermediate of the isoleucine biosynthetic pathway, α-keto-β-methylvalerate, could also alleviate the growth inhibition caused by Hcy. Analysis of amino acid pools in Hcy-treated cells revealed that alanine, valine, and glutamate levels are depleted. Isoleucine could reverse the effects of Hcy on the cytoplasmic pools of valine and alanine. Supplementation of the culture medium with alanine gave partial relief from the inhibitory effects of Hcy. Enzyme assays revealed that the first step of the isoleucine biosynthetic pathway, catalyzed by threonine deaminase, was sensitive to inhibition by Hcy. The gene encoding threonine deaminase, ilvA, was found to be transcribed at higher levels in the presence of Hcy. Overexpression of the ilvA gene from a plasmid could overcome Hcy-mediated growth inhibition. Together, these data indicate that in E. coli Hcy toxicity is caused by a perturbation of branched-chain amino acid biosynthesis that is caused, at least in part, by the inhibition of threonine deaminase.

Endotoxin Alteration of the Mucopolysaccharide Blood Vessel Coating in Rats

1974 ◽  
Vol 32 ◽  
pp. 148-149
Author(s):  
D. E. Philpott ◽  
A. Takahashi
Keyword(s):  
Skeletal Muscle ◽  
Endothelial Cells ◽  
Salivary Gland ◽  
Carotid Artery ◽  
Basement Membrane ◽  
Coronary Vessels ◽  
Ruthenium Red ◽  
E Coli ◽  
Old Rats ◽  
The Brain

Two month, eight month and two year old rats were treated with 10 or 20 mg/kg of E. Coli endotoxin I. P. The eight month old rats proved most resistant to the endotoxin. During fixation the aorta, carotid artery, basil arartery of the brain, coronary vessels of the heart, inner surfaces of the heart chambers, heart and skeletal muscle, lung, liver, kidney, spleen, brain, retina, trachae, intestine, salivary gland, adrenal gland and gingiva were treated with ruthenium red or alcian blue to preserve the mucopolysaccharide (MPS) coating. Five, 8 and 24 hrs of endotoxin treatment produced increasingly marked capillary damage, disappearance of the MPS coating, edema, destruction of endothelial cells and damage to the basement membrane in the liver, kidney and lung.

Ribosome Structural Organization

1974 ◽  
Vol 32 ◽  
pp. 332-333
Author(s):  
James A. Lake
Keyword(s):  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Small Subunit ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
Specific Antibodies ◽  
X Ray ◽  
E Coli ◽  
Complete Sequences

The understanding of ribosome structure has advanced considerably in the last several years. Biochemists have characterized the constituent proteins and rRNA's of ribosomes. Complete sequences have been determined for some ribosomal proteins and specific antibodies have been prepared against all E. coli small subunit proteins. In addition, a number of naturally occuring systems of three dimensional ribosome crystals which are suitable for structural studies have been observed in eukaryotes. Although the crystals are, in general, too small for X-ray diffraction, their size is ideal for electron microscopy.

Sites of Adsorption of the Bacteriophages T3 and T5 on the Wall of Escherichia Coli B.

1967 ◽  
Vol 25 ◽  
pp. 96-97
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Electron Microscope ◽  
Uranyl Acetate ◽  
E Coli ◽  
Receptor Sites ◽  
Rigid Cell Wall ◽  
Host Cell Surface ◽  
Bacterial Viruses ◽  
Escherichia Coli B

Bacterial viruses adsorb specifically to receptors on the host cell surface. Although the chemical composition of some of the cell wall receptors for bacteriophages of the T-series has been described and the number of receptor sites has been estimated to be 150 to 300 per E. coli cell, the localization of the sites on the bacterial wall has been unknown.When logarithmically growing cells of E. coli are transferred into a medium containing 20% sucrose, the cells plasmolize: the protoplast shrinks and becomes separated from the somewhat rigid cell wall. When these cells are fixed in 8% Formaldehyde, post-fixed in OsO4/uranyl acetate, embedded in Vestopal W, then cut in an ultramicrotome and observed with the electron microscope, the separation of protoplast and wall becomes clearly visible, (Fig. 1, 2). At a number of locations however, the protoplasmic membrane adheres to the wall even under the considerable pull of the shrinking protoplast. Thus numerous connecting bridges are maintained between protoplast and cell wall. Estimations of the total number of such wall/membrane associations yield a number of about 300 per cell.

Emigration of neutrophils in the central nervous system

1983 ◽  
Vol 41 ◽  
pp. 788-789
Author(s):  
John L.Beggs ◽  
John D. Waggener ◽  
Wanda Miller ◽  
Jane Watkins
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Osmium Tetroxide ◽  
White Blood Cells ◽  
Arterial Perfusion ◽  
E Coli ◽  
Intracisternal Injection ◽  
The Central Nervous System ◽  
Brain And Spinal Cord ◽  
Interendothelial Junctions

Studies using mesenteric and ear chamber preparations have shown that interendothelial junctions provide the route for neutrophil emigration during inflammation. The term emigration refers to the passage of white blood cells across the endothelium from the vascular lumen. Although the precise pathway of transendo- thelial emigration in the central nervous system (CNS) has not been resolved, the presence of different physiological and morphological (tight junctions) properties of CNS endothelium may dictate alternate emigration pathways.To study neutrophil emigration in the CNS, we induced meningitis in guinea pigs by intracisternal injection of E. coli bacteria.In this model, leptomeningeal inflammation is well developed by 3 hr. After 3 1/2 hr, animals were sacrificed by arterial perfusion with 3% phosphate buffered glutaraldehyde. Tissues from brain and spinal cord were post-fixed in 1% osmium tetroxide, dehydrated in alcohols and propylene oxide, and embedded in Epon. Thin serial sections were cut with diamond knives and examined in a Philips 300 electron microscope.

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