scholarly journals Accumulation of α-Keto Acids as Essential Components in Cyanide Assimilation by Pseudomonas fluorescens NCIMB 11764

1998 ◽  
Vol 64 (11) ◽  
pp. 4452-4459 ◽  
Author(s):  
Daniel A. Kunz ◽  
Jui-Lin Chen ◽  
Guangliang Pan
Keyword(s):  
Pseudomonas Fluorescens ◽  
Culture Fluid ◽  
Maximal Activity ◽  
Resonance Spectroscopy ◽  
Keto Acid ◽  
Growth Substrate ◽  
Reaction Products ◽  
Cell Extracts ◽  
Keto Acids ◽  
Essential Components

ABSTRACT Pyruvate (Pyr) and α-ketoglutarate (αKg) accumulated when cells of Pseudomonas fluorescens NCIMB 11764 were cultivated on growth-limiting amounts of ammonia or cyanide and were shown to be responsible for the nonenzymatic removal of cyanide from culture fluids as previously reported (J.-L. Chen and D. A. Kunz, FEMS Microbiol. Lett. 156:61–67, 1997). The accumulation of keto acids in the medium paralleled the increase in cyanide-removing activity, with maximal activity (760 μmol of cyanide removed min−1 ml of culture fluid−1) being recovered after 72 h of cultivation, at which time the keto acid concentration was 23 mM. The reaction products that formed between the biologically formed keto acids and cyanide were unambiguously identified as the corresponding cyanohydrins by 13C nuclear magnetic resonance spectroscopy. Both the Pyr and α-Kg cyanohydrins were further metabolized by cell extracts and served also as nitrogenous growth substrates. Radiotracer experiments showed that CO2 (and NH3) were formed as enzymatic conversion products, with the keto acid being regenerated as a coproduct. Evidence that the enzyme responsible for cyanohydrin conversion is cyanide oxygenase, which was shown previously to be required for cyanide utilization, is based on results showing that (i) conversion occurred only when extracts were induced for the enzyme, (ii) conversion was oxygen and reduced-pyridine nucleotide dependent, and (iii) a mutant strain defective in the enzyme was unable to grow when it was provided with the cyanohydrins as a growth substrate. Pyr and αKg were further shown to protect cells from cyanide poisoning, and excretion of the two was directly linked to utilization of cyanide as a growth substrate. The results provide the basis for a new mechanism of cyanide detoxification and assimilation in which keto acids play an essential role.

THE INHIBITION OF KETO ACID OXIDATION BY PYOCYANINE

1957 ◽  
Vol 3 (2) ◽  
pp. 313-318 ◽  
Author(s):  
J. J. R. Campbell ◽  
A. M. MacQuillan ◽  
B. A. Eagles ◽  
R. A. Smith
Keyword(s):  
Escherichia Coli ◽  
Cell Membrane ◽  
Pseudomonas Fluorescens ◽  
Acid Level ◽  
Divalent Cations ◽  
Acid Oxidation ◽  
Keto Acid ◽  
Proteus Vulgaris ◽  
Whole Cells ◽  
Cell Extracts

When tested against Pseudomonas fluorescens, pyocyanine was found to stop the oxidation of a number of substrates at the keto acid level. This inhibition could be reversed by the addition of divalent cations. Of these, magnesium was most effective. The pigment was found to be similarly effective against the oxidations of Proteus vulgaris. Whole cells of Escherichia coli were not affected by the dye, whereas cell extracts were, indicating that the dye did not penetrate the cell membrane.

scholarly journals CDP-2,3-Di-O-Geranylgeranyl-sn-Glycerol:l-Serine O-Archaetidyltransferase (Archaetidylserine Synthase) in the Methanogenic Archaeon Methanothermobacter thermautotrophicus

2003 ◽  
Vol 185 (4) ◽  
pp. 1181-1189 ◽  
Author(s):  
Hiroyuki Morii ◽  
Yosuke Koga
Keyword(s):  
Substrate Specificity ◽  
Maximal Activity ◽  
Chemical Degradation ◽  
Reaction Products ◽  
Gene Encoding ◽  
Substrate Analogs ◽  
Cell Extracts ◽  
Phosphatidylserine Synthase ◽  
Methanothermobacter Thermautotrophicus ◽  
Triton X

ABSTRACT CDP-2,3-di-O-geranylgeranyl-sn-glycerol:l-serine O-archaetidyltransferase (archaetidylserine synthase) activity in cell extracts of Methanothermobacter thermautotrophicus cells was characterized. The enzyme catalyzed the formation of unsaturated archaetidylserine from CDP-unsaturated archaeol and l-serine. The identity of the reaction products was confirmed by thin-layer chromatography, fast atom bombardment-mass spectrum analysis, and chemical degradation. The enzyme showed maximal activity in the presence of 10 mM Mn2+ and 1% Triton X-100. Among various synthetic substrate analogs, both enantiomers of CDP-unsaturated archaeols with ether-linked geranylgeranyl chains and CDP-saturated archaeol with ether-linked phytanyl chains were similarly active toward the archaetidylserine synthase. The activity on the ester analog of the substrate was two to three times higher than that on the corresponding ether-type substrate. The activity of d-serine with the enzyme was 30% of that observed for l-serine. A trace amount of an acid-labile, unsaturated archaetidylserine intermediate was detected in the cells by a pulse-labeling experiment. A gene (MT1027) in M. thermautotrophicus genome annotated as the gene encoding phosphatidylserine synthase was found to be homologous to Bacillus subtilis pssA but not to Escherichia coli pssA. The substrate specificity of phosphatidylserine synthase from B. subtilis was quite similar to that observed for the M. thermautotrophicus archaetidylserine synthase, while the E. coli enzyme had a strong preference for CDP-1,2-diacyl-sn-glycerol. It was concluded that M. thermautotrophicus archaetidylserine synthase belongs to subclass II phosphatidylserine synthase (B. subtilis type) on the basis of not only homology but also substrate specificity and some enzymatic properties. The possibility that a gene encoding the subclass II phosphatidylserine synthase might be transferred from a bacterium to an ancestor of methanogens is discussed.

On the Chemistry of Tetrabenzyl Thiuram Disulfide and Tetramethyl Thiuram Disulfide with Bis (Triethoxysilylpropyl) Tetrasulfide in Silica Compounds

2003 ◽  
Vol 76 (4) ◽  
pp. 876-891 ◽  
Author(s):  
R. N. Datta ◽  
A. G. Talma ◽  
S. Datta ◽  
P. G. J. Nieuwenhuis ◽  
W. J. Nijenhuis ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Succinic Anhydride ◽  
Dynamic Properties ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Negative Effect ◽  
Higher Temperature ◽  
Analytical Tools

Abstract The use of thiurams such as Tetramethyl thiuram disulfide (TMTD) or Tetrabenzyl thiuram disulfide (TBzTD) has been explored to achieve higher cure efficiency. The studies suggest that a clear difference exists between the effect of TMTD versus TBzTD. TMTD reacts with Bis (triethoxysilylpropyl) tetrasulfide (TESPT) and this reaction can take place even at room temperature. On the other hand, the reaction of TBzTD with TESPT is slow and takes place only at higher temperature. High Performance Liquid Chromatography (HPLC) with mass (MS) detection, Nuclear Magnetic Resonance Spectroscopy (NMR) and other analytical tools have been used to understand the differences between the reaction of TMTD and TESPT versus TBzTD and TESPT. The reaction products originating from these reactions are also identified. These studies indicate that unlike TMTD, TBzTD improves the cure efficiency allowing faster cure without significant effect on processing characteristics as well as dynamic properties. The loading of TESPT is reduced in a typical Green tire compound and the negative effect on viscosity is repaired by addition of anhydrides, such as succinic anhydride, maleic anhydride, etc.

scholarly journals Formation of flavorant–propylene Glycol Adducts With Novel Toxicological Properties in Chemically Unstable E-Cigarette Liquids

2018 ◽  
Vol 21 (9) ◽  
pp. 1248-1258 ◽  
Author(s):  
Hanno C Erythropel ◽  
Sairam V Jabba ◽  
Tamara M DeWinter ◽  
Melissa Mendizabal ◽  
Paul T Anastas ◽  
...  
Keyword(s):  
Propylene Glycol ◽  
Electronic Cigarettes ◽  
Aqueous Media ◽  
Chemical Species ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Chemical Systems ◽  
Toxicological Effects ◽  
Wide Range ◽  
Irritant Receptors

Abstract Introduction “Vaping” electronic cigarettes (e-cigarettes) is increasingly popular with youth, driven by the wide range of available flavors, often created using flavor aldehydes. The objective of this study was to examine whether flavor aldehydes remain stable in e-cigarette liquids or whether they undergo chemical reactions, forming novel chemical species that may cause harm to the user. Methods Gas chromatography was used to determine concentrations of flavor aldehydes and reaction products in e-liquids and vapor generated from a commercial e-cigarette. Stability of the detected reaction products in aqueous media was monitored by ultraviolet spectroscopy and nuclear magnetic resonance spectroscopy, and their effects on irritant receptors determined by fluorescent calcium imaging in HEK-293T cells. Results Flavor aldehydes including benzaldehyde, cinnamaldehyde, citral, ethylvanillin, and vanillin rapidly reacted with the e-liquid solvent propylene glycol (PG) after mixing, and upward of 40% of flavor aldehyde content was converted to flavor aldehyde PG acetals, which were also detected in commercial e-liquids. Vaping experiments showed carryover rates of 50%–80% of acetals to e-cigarette vapor. Acetals remained stable in physiological aqueous solution, with half-lives above 36 hours, suggesting they persist when inhaled by the user. Acetals activated aldehyde-sensitive TRPA1 irritant receptors and aldehyde-insensitive TRPV1 irritant receptors. Conclusions E-liquids are potentially reactive chemical systems in which new compounds can form after mixing of constituents and during storage, as demonstrated here for flavor aldehyde PG acetals, with unexpected toxicological effects. For regulatory purposes, a rigorous process is advised to monitor the potentially changing composition of e-liquids and e-vapors over time, to identify possible health hazards. Implications This study demonstrates that e-cigarette liquids can be chemically unstable, with reactions occurring between flavorant and solvent components immediately after mixing at room temperature. The resulting compounds have toxicological properties that differ from either the flavorants or solvent components. These findings suggest that the reporting of manufacturing ingredients of e-liquids is insufficient for a safety assessment. The establishment of an analytical workflow to detect newly formed compounds in e-liquids and their potential toxicological effects is imperative for regulatory risk analysis.

scholarly journals Convenient Genetic Encoding of Phenylalanine Derivatives through Their α-Keto Acid Precursors

Biomolecules ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1358
Author(s):  
Li Liu ◽  
Bohao Wang ◽  
Sheng Li ◽  
Fengyuan Xu ◽  
Qi He ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genetic Code ◽  
Fluorescent Proteins ◽  
Coli Strain ◽  
Keto Acid ◽  
Phenylpyruvic Acid ◽  
Genetic Encoding ◽  
Keto Acids ◽  
Genetic Code Expansion ◽  
And Function

The activity and function of proteins can be improved by incorporation of non-canonical amino acids (ncAAs). To avoid the tedious synthesis of a large number of chiral phenylalanine derivatives, we synthesized the corresponding phenylpyruvic acid precursors. Escherichia coli strain DH10B and strain C321.ΔA.expΔPBAD were selected as hosts for phenylpyruvic acid bioconversion and genetic code expansion using the MmPylRS/pyltRNACUA system. The concentrations of keto acids, PLP and amino donors were optimized in the process. Eight keto acids that can be biotransformed and their coupled genetic code expansions were identified. Finally, the genetic encoded ncAAs were tested for incorporation into fluorescent proteins with keto acids.

Transport of alpha-keto analogues of amino acids across blood-brain barrier in rats

1982 ◽  
Vol 243 (4) ◽  
pp. E272-E277
Author(s):  
A. R. Conn ◽  
R. D. Steele
Keyword(s):  
Blood Brain Barrier ◽  
Transport System ◽  
Ketone Bodies ◽  
Brain Barrier ◽  
Sodium Pentobarbital ◽  
Keto Acid ◽  
Dual Isotope ◽  
Common System ◽  
Blood Brain ◽  
Keto Acids

The transport of 14C-labeled alpha-keto acids across the blood-brain barrier (BBB) was studied in rats anesthetized with sodium pentobarbital using a modification of a single-injection dual-isotope technique. alpha-Keto acids were found to cross the BBB via a saturable carrier-mediated transport system that may be specific based on lack of inhibition by glucose, isoleucine, and ketone bodies on the uptake of tracer levels of 14C-labeled alpha-keto acids. alpha-Ketobutyrate and alpha-keto-gamma-methiolbutyrate, both straight chain keto acids, and alpha-ketoisocaproate, a branched-chain keto acid, appeared to cross the barrier by a common carrier based on cross-inhibition studies. Aromatic keto acids had no effect on the uptake of tracer levels of these 14C-keto acids. The Km of transport of alpha-ketobutyrate, alpha-ketoisocaproate, and alpha-keto-gamma-methiolbutyrate, was 0.11, 0.60, and 0.33 mM, respectively. The corresponding Vmax was 15.7, 73.3, and 30.2 nmol . g-1 . min-1. Phenylpyruvate was found not to cross the BBB. Inhibition of brain uptake of alpha-keto acids by propionate and pyruvate, and not by DL-beta-hydroxybutyrate suggests that alpha-keto acids and monocarboxylic acids are transported either via a common system independent of ketone bodies or share an affinity with a monocarboxylic acid and an alpha-keto acid transport system.

Transamination of branched-chain keto acids by isolated perfused rat kidney.

1978 ◽  
Vol 235 (1) ◽  
pp. E47
Author(s):  
W E Mitch ◽  
W Chan
Keyword(s):  
Amino Acids ◽  
Rat Kidney ◽  
Branched Chain Amino Acids ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Perfused Rat Kidney ◽  
Branched Chain ◽  
Branched Chain Keto Acids ◽  
Isolated Rat

Isolated rat kidney perfused without substrate released serine, glycine, and taurine, and substantially smaller amounts of other amino acids. When branched-chain keto acids were added, the corresponding amino acids were released at rates amounting to 15-25% of keto acid disappearance. Perfusion with 2 mM alpha-keto-isovalerate or alpha-keto-beta-methylvalerate caused an increased glucose release amounting to 18-23% of keto acid disappearance. The activity of branched-chain amino acid transferase (BATase) was significantly stimulated by perfusion with the analogue of leucine, but not by perfusion with alpha-ketoglutarate, the analogues of valine or isoleucine, or with leucine itself. These findings document that the kidney converts branched-chain keto acids in part to the corresponding amino acids and suggest that the keto analogue of leucine may be involved in the control of renal BATase activity, thereby indirectly regulating the metabolism of branched-chain amino acids.

scholarly journals Mode of action of endoglucanase III from Trichoderma reesei

1993 ◽  
Vol 289 (3) ◽  
pp. 867-873 ◽  
Author(s):  
R Macarrón ◽  
C Acebal ◽  
M P Castillón ◽  
J M Domínguez ◽  
I de la Mata ◽  
...  
Keyword(s):  
New Orleans ◽  
Trichoderma Reesei ◽  
Culture Medium ◽  
Ph Dependence ◽  
Maximal Activity ◽  
Cleavage Sites ◽  
Reaction Products ◽  
Binding Model ◽  
Independent Evidence ◽  
Affinity Labelling

Endoglucanase III (EG III) was purified to homogeneity from the culture medium of Trichoderma reesei QM 9414. It has a molecular mass of 48 kDa, and an isoelectric point of 5.1. Maximal activity was observed between pH4 and 5. Celloligosaccharides and their chromophoric derivatives were used as substrates, and the reaction products were analysed by quantitative h.p.l.c. Nucleophilic competition experiments (between methanol and water) allowed unequivocal assessment of cleavage sites. EG III preferentially released cellobiose (or the corresponding glycoside) from the reducing end of the higher cellodextrins. A putative binding model containing five subsites is proposed. The pH-dependence of 4′-methylumbelliferyl beta-cellotrioside hydrolysis indicates the presence of a protonated group with a pK 5.5 in the reaction mechanism, and the possible involvement of a carboxy group is corroborated by a temperature study (delta Hion = -15.9 J/mol). This, together with independent evidence from affinity-labelling experiments [Tomme, Macarrón and Claeyssens (1991) Cellulose '91, New Orleans, Abstr. 32] and n.m.r. studies [Gebbler, Gilkes, Claeyssens, Wilson, Béguin, Wakarchuk, Kilburn, Miller, Warren and Withers (1992) J. Biol. Chem. 267, 12559-12561], favours the assumption of a lysozyme-type (retention of configuration, two essential carboxy groups) mechanism for this family A cellulase.

scholarly journals Degradation of Phenol via Meta Cleavage Pathway by Pseudomonas fluorescens PU1

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Md. Mahiudddin ◽  
A. N. M. Fakhruddin ◽  
Abdullah-Al-Mahin
Keyword(s):  
Phenolic Compounds ◽  
Pseudomonas Fluorescens ◽  
Phenol Degradation ◽  
Carbon Sources ◽  
Soil Microflora ◽  
Ring Cleavage ◽  
Cell Extracts ◽  
Polluted Sites ◽  
Important Means ◽  
Biodegradation Efficiency

Degradation of phenolics by members of soil microflora is an important means by which these substances are removed from the environment thus reducing environmental pollution. Biodegradation by microorganisms offers unique opportunities to destroy or render phenolic compounds. A bacterium, PU1, identified as Pseudomonas fluorescens PU1, was investigated for its ability to grow on and degrade phenols as sole carbon sources in aerobic shaking batch culture. The organism degraded up to 1000 ppm of phenol using meta cleavage pathway. The pathways for phenol degradation were proposed by the identification of metabolites and assay of ring cleavage enzymes in cell extracts. Phenol was degraded via catechol with subsequent metaring cleavage. Cell growth increased as the phenol concentrations increased up to 1000 ppm phenol. The biodegradation efficiency, degradation extent, and metabolic pathway of phenol were determined to provide useful clues for further application of this isolate in the engineered bioremediation systems. The paper's results suggest that Pseudomonas fluorescens PU1 strain could be a good candidate for remediation of phenol contaminants from heavily polluted sites.

Sign in / Sign up

Export Citation Format

Share Document