scholarly journals Bacterial catabolism of threonine. Threonine degradation initiated by l-threonine acetaldehyde-lyase (aldolase) in species of Pseudomonas

1977 ◽  
Vol 166 (2) ◽  
pp. 209-216 ◽  
Author(s):  
Stephen C. Bell ◽  
John M. Turner
Keyword(s):  
Reductase Activity ◽  
Growth Conditions ◽  
Serine Hydroxymethyltransferase ◽  
Threonine Aldolase ◽  
Highly Active ◽  
Activity Ratios ◽  
Exclusion Chromatography ◽  
Mammalian Origin ◽  
Aldolase Activity ◽  
Single Enzyme

1. The route of l-threonine degradation was studied in four strains of the genus Pseudomonas able to grow on the amino acid and selected because of their high l-threonine aldolase activity. Growth and manometric results were consistent with the cleavage of l-threonine to acetaldehyde+glycine and their metabolism via acetate and serine respectively. 2. l-Threonine aldolases in these bacteria exhibited pH optima in the range 8.0–8.7 and Km values for the substrate of 5–10mm. Extracts exhibited comparable allo-l-threonine aldolase activities, Km values for this substrate being 14.5–38.5mm depending on the bacterium. Both activities were essentially constitutive. Similar activity ratios in extracts, independent of growth conditions, suggested a single enzyme. The isolate Pseudomonas D2 (N.C.I.B. 11097) represents the best source of the enzyme known. 3. Extracts of all the l-threonine-grown pseudomonads also possessed a CoA-independent aldehyde dehydrogenase, the synthesis of which was induced, and a reversible alcohol dehydrogenase. The high acetaldehyde reductase activity of most extracts possibly resulted in the underestimation of acetaldehyde dehydrogenase. 4. l-Serine dehydratase formation was induced by growth on l-threonine or acetate+glycine. Constitutively synthesized l-serine hydroxymethyltransferase was detected in extracts of Pseudomonas strains D2 and F10. The enzyme could not be detected in strains A1 and N3, probably because of a highly active ‘formaldehyde-utilizing’ system. 5. Ion-exchange and molecular exclusion chromatography supported other evidence that l-threonine aldolase and allo-l-threonine aldolase activities were catalysed by the same enzyme but that l-serine hydroxymethyltransferase was distinct and different. These results contrast with the specificities of some analogous enzymes of mammalian origin.

scholarly journals l -Threonine aldolase, serine hydroxymethyltransferase and fungal alanine racemase

2001 ◽  
Vol 268 (24) ◽  
pp. 6508-6525 ◽  
Author(s):  
Roberto Contestabile ◽  
Alessandro Paiardini ◽  
Stefano Pascarella ◽  
Martino L. di Salvo ◽  
Simona D'Aguanno ◽  
...  
Keyword(s):  
Serine Hydroxymethyltransferase ◽  
Alanine Racemase ◽  
Threonine Aldolase

RESPIRATORY CARRIERS AND THE NATURE OF THE REDUCED DIPHOSPHOPYRIDINE NUCLEOTIDE OXIDASE SYSTEM IN XANTHOMONAS PHASEOLI

1960 ◽  
Vol 38 (1) ◽  
pp. 79-93 ◽  
Author(s):  
R. M. Hochster ◽  
C. G. Nozzolillo
Keyword(s):  
Cytochrome C ◽  
Reductase Activity ◽  
Inorganic Ions ◽  
Product Formation ◽  
Intact Cells ◽  
Oxidase System ◽  
Clear Cut ◽  
Highly Active ◽  
Inhibitor Study ◽  
Terminal Oxidation

Intact cells and cell-free extracts of the phytopathogenic organism Xanthomonas phaseoli have been shown to contain flavoprotein and the respiratory carriers: cytochrome b1, cytochrome a1, and cytochrome a2. The reduced forms of these respiratory pigments are produced upon addition to a clear extract of substrate amounts of DPNH.The highly active DPNH oxidase system in extracts of this organism has been studied as to requirements for inorganic ions, optimum pH, product formation, distribution, and solubilization. Carbon monoxide inhibits the terminal oxidation system; this effect is reversed by bright light.An inhibitor study has shown members of the phenothiazine family of compounds to be most effective, followed by amytal, cyanide, BAL, atabrine, and pCMB. The most notable of the substances which did not inhibit were antimycin A, one of the quinoline-N-oxides, and azide.The possibility exists that H2O2may also be formed during the oxidation of DPNH although clear-cut evidence for its presence was difficult to obtain. X. phaseoli extracts do not contain a DPNH peroxidase. They exhibit, however, some DPNH – cytochrome c reductase activity which is believed to be quite independent of the DPNH oxidase system. The extracts are devoid of cytochrome c oxidase activity although they contain a respiratory system which readily oxidizes p-phenylenediamine.

Nitrogen Assimilation Enzyme Activities in Witchweed (Striga) in Hosts Presence and Absence

Weed Science ◽  
1996 ◽  
Vol 44 (2) ◽  
pp. 224-232 ◽  
Author(s):  
Imuetinyan Igbinnosa ◽  
Patrick A. Thalouarn
Keyword(s):  
Host Plant ◽  
Enzyme Activities ◽  
Host Plants ◽  
Nitrogen Assimilation ◽  
Reductase Activity ◽  
Growth Conditions ◽  
Plant Growth And Development ◽  
Continuous Darkness ◽  
N Assimilation ◽  
Insight Into

N fertilizers suppress witchweed plant growth and development, thus reducing the severity of parasite attack and increasing host yield simultaneously. However, the underlying physiological mode of N action occurring within the parasite cells remains largely unknown. This study aims at screening for the effects of N forms and different growth conditions on some N assimilation enzymes in witchweed seedlings grown aseptically without host plant, and in pots with host plants. Results show that supply of N in NH4+or urea forms resulted in 83 to 92% reduction in nitrate reductase activity (NRc), compared with control. Increasing NO3−concentrations from 0 mM to 100 mM, led to a corresponding increase in NRc in giant witchweed. NRc of giant witchweed seedlings grown under light and dark cycles were about 270 times higher than seedlings grown in continuous darkness. A combination of NH4+and NO3−, resulted in increased giant witchweed NRc, compared with NH4+or NO3−supplied singly. Highest shoot development and NRc was at NH4+and NO3−ratio 1:1, followed by ratios 1:3, 3:1, 0:1, and 1:0, respectively. Addition of N in soils resulted in increased NRc, followed by rapid deterioration and death of giant witchweed plants. NRc, GSc, and GDHc in witchweed, maize, cowpea, and tobacco were affected by diurnal fluctuations with higher enzyme activities occurring during the day than at night. Higher GSc than GDHc suggests that NH4+assimilation occurs mainly through the GS pathway in witchweed plants. NRc and GDHc were two and four times higher in giant witchweed grown in aseptic media without host plant, than that grown in potted soils with host plants. These findings provide insight into the physiological mode of N action and their implications on witchweed control.

Measurement of l-Threonine Aldolase Activity in Rat Liver

1979 ◽  
Vol 7 (6) ◽  
pp. 1274-1276 ◽  
Author(s):  
MICHAEL I. BIRD ◽  
PETER B. NUNN
Keyword(s):  
Rat Liver ◽  
Threonine Aldolase ◽  
Aldolase Activity

scholarly journals Novel Alkylsulfatases Required for Biodegradation of the Branched Primary Alkyl Sulfate Surfactant 2-Butyloctyl Sulfate

2002 ◽  
Vol 68 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Andrew J. Ellis ◽  
Stephen G. Hales ◽  
Naheed G. A. Ur-Rehman ◽  
Graham F. White
Keyword(s):  
Gel Electrophoresis ◽  
Chromatographic Analysis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Hydrolytic Activity ◽  
Growth Conditions ◽  
Alkyl Sulfate ◽  
Activated Sewage Sludge ◽  
Single Enzyme ◽  
Common Perception

ABSTRACT Recent reports show that contrary to common perception, branched alkyl sulfate surfactants are readily biodegradable in standard biodegradability tests. We report here the isolation of bacteria capable of biodegrading 2-butyloctyl sulfate and the identification of novel enzymes that initiate the process. Enrichment culturing from activated sewage sludge yielded several strains capable of growth on 2-butyloctyl sulfate. Of these, two were selected for further study and identified as members of the genus Pseudomonas. Strain AE-A was able to utilize either sodium dodecyl sulfate (SDS) or 2-butyloctyl sulfate as a carbon and energy source for growth, but strain AE-D utilized only the latter. Depending on growth conditions, strain AE-A produced up to three alkylsulfatases, as shown by polyacrylamide gel electrophoresis zymography. Growth on either SDS or 2-butyloctyl sulfate or in nutrient broth produced an apparently constitutive, nonspecific primary alkylsulfatase, AP1, weakly active on SDS and on 2-butyloctyl sulfate. Growth on 2-butyloctyl sulfate produced a second enzyme, AP2, active on 2-butyloctyl sulfate but not on SDS, and growth on SDS produced a third enzyme, AP3, active on SDS but not on 2-butyloctyl sulfate. In contrast, strain AE-D, when grown on 2-butyloctyl sulfate (no growth on SDS), produced a single enzyme, DP1, active on 2-butyloctyl sulfate but not on SDS. DP1 was not produced in broth cultures. DP1 was induced when residual 2-butyloctyl sulfate was present in the growth medium, but the enzyme disappeared when the substrate was exhausted. Gas chromatographic analysis of products of incubating 2-butyloctyl sulfate with DP1 in gels revealed the formation of 2-butyloctanol, showing the enzyme to be a true sulfatase. In contrast, Pseudomonas sp. strain C12B, well known for its ability to degrade linear SDS, was unable to grow on 2-butyloctyl sulfate, and its alkylsulfatases responsible for initiating the degradation of SDS by releasing the parent alcohol exhibited no hydrolytic activity on 2-butyloctyl sulfate. DP1 and the analogous AP2 are thus new alkylsulfatase enzymes with novel specificity toward 2-butyloctyl sulfate.

scholarly journals A soluble 3-hydroxy-3-methylglutaryl-CoA reductase in the protozoan Trypanosoma cruzi

1997 ◽  
Vol 324 (2) ◽  
pp. 619-626 ◽  
Author(s):  
Javier PEÑA-DÍAZ ◽  
Andrea MONTALVETTI ◽  
Ana CAMACHO ◽  
Claribel GALLEGO ◽  
Luis M. RUIZ-PEREZ ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Reductase Activity ◽  
Active Form ◽  
Single Copy ◽  
Enzymic Activity ◽  
Highly Active ◽  
Frame Sequence ◽  
Isolation And Characterization ◽  
Cell Extracts ◽  
Coa Reductase

We report the isolation and characterization of a genomic clone containing the open reading frame sequence for 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase from Trypanosoma cruzi, the causative agent of Chagas' disease. The protozoan gene encoded for a smaller polypeptide than the rest of the genes described from eukaryotic organisms and the deduced amino acid sequence could be aligned with the C-terminal half of animal and plant reductases exhibiting pronounced similarity to other eukaryotic counterparts. Further examination of the 5′ flanking region by cDNA analysis and establishment of the splice acceptor sites clearly indicated that the corresponding mRNA apparently lacks sequences encoding a membrane N-terminal domain. The reductase gene is a single copy and is located on a chromosome of 1.36 Mb as determined by contour-clamped homogeneous electric field electrophoresis. The overall cellular distribution of enzymic activity was investigated after differential centrifugation of Trypanosoma cell extracts. Reductase activity was primarily associated with the cellular soluble fraction because 95% of the total cellular activity was recovered in the supernatant and was particularly sensitive to proteolytic inactivation. Furthermore the enzyme can be efficiently overexpressed in a highly active form by using the expression vector pET-11c. Thus Trypanosoma cruziHMG-CoA reductase is unique in the sense that it totally lacks the membrane-spanning sequences present in all eukaryotic HMG-CoA reductases so far characterized.

scholarly journals Disruption of the SHM2 gene, encoding one of two serine hydroxymethyltransferase isoenzymes, reduces the flux from glycine to serine in Ashbya gossypii

2003 ◽  
Vol 369 (2) ◽  
pp. 263-273 ◽  
Author(s):  
Christina SCHLÜPEN ◽  
Maria A. SANTOS ◽  
Ulrike WEBER ◽  
Albert de GRAAF ◽  
José L. REVUELTA ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Specific Activity ◽  
Serine Hydroxymethyltransferase ◽  
Detectable Effect ◽  
Ashbya Gossypii ◽  
Gene Encoding ◽  
13C Labelling ◽  
Glycine Metabolism ◽  
Aldolase Activity

Riboflavin overproduction in the ascomycete Ashbya gossypii is limited by glycine, a precursor of purine biosynthesis, and therefore an indicator of glycine metabolism. Disruption of the SHM2 gene, encoding a serine hydroxymethyltransferase, resulted in a significant increase in riboflavin productivity. Determination of the enzyme's specific activity revealed a reduction from 3m-units/mg of protein to 0.5m-unit/mg protein. The remaining activity was due to an isoenzyme encoded by SHM1, which is probably mitochondrial. A hypothesis proposed to account for the enhanced riboflavin overproduction of SHM2-disrupted mutants was that the flux from glycine to serine was reduced, thus leading to an elevated supply with the riboflavin precursor glycine. Evidence for the correctness of that hypothesis was obtained from 13C-labelling experiments. When 500μM 99% [1-13C]threonine was fed, more than 50% of the label was detected in C-1 of glycine resulting from threonine aldolase activity. More than 30% labelling determined in C-1 of serine can be explained by serine synthesis via serine hydroxymethyltransferase. Knockout of SHM1 had no detectable effect on serine labelling, but disruption of SHM2 led to a decrease in serine (2—5%) and an increase in glycine (59—67%) labelling, indicating a changed carbon flux.

scholarly journals Malonyl-Coenzyme A Reductase in the Modified 3-Hydroxypropionate Cycle for Autotrophic Carbon Fixation in Archaeal Metallosphaera and Sulfolobus spp.

2006 ◽  
Vol 188 (24) ◽  
pp. 8551-8559 ◽  
Author(s):  
Birgit Alber ◽  
Marc Olinger ◽  
Annika Rieder ◽  
Daniel Kockelkorn ◽  
Björn Jobst ◽  
...  
Keyword(s):  
Amino Acid ◽  
Carbon Fixation ◽  
Coenzyme A ◽  
Reductase Activity ◽  
Growth Conditions ◽  
Significant Similarity ◽  
Semialdehyde Dehydrogenase ◽  
Malonyl Coa ◽  
Taxonomic Groups ◽  
Coa Reductase

ABSTRACT Autotrophic members of the Sulfolobales (Crenarchaeota) contain acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the CO2 fixation enzyme and use a modified 3-hydroxypropionate cycle to assimilate CO2 into cell material. In this central metabolic pathway malonyl-CoA, the product of acetyl-CoA carboxylation, is further reduced to 3-hydroxypropionate. Extracts of Metallosphaera sedula contained NADPH-specific malonyl-CoA reductase activity that was 10-fold up-regulated under autotrophic growth conditions. Malonyl-CoA reductase was partially purified and studied. Based on N-terminal amino acid sequencing the corresponding gene was identified in the genome of the closely related crenarchaeum Sulfolobus tokodaii. The Sulfolobus gene was cloned and heterologously expressed in Escherichia coli, and the recombinant protein was purified and studied. The enzyme catalyzes the following reaction: malonyl-CoA + NADPH + H+ → malonate-semialdehyde + CoA + NADP+. In its native state it is associated with small RNA. Its activity was stimulated by Mg2+ and thiols and inactivated by thiol-blocking agents, suggesting the existence of a cysteine adduct in the course of the catalytic cycle. The enzyme was specific for NADPH (Km = 25 μM) and malonyl-CoA (Km = 40 μM). Malonyl-CoA reductase has 38% amino acid sequence identity to aspartate-semialdehyde dehydrogenase, suggesting a common ancestor for both proteins. It does not exhibit any significant similarity with malonyl-CoA reductase from Chloroflexus aurantiacus. This shows that the autotrophic pathway in Chloroflexus and Sulfolobaceae has evolved convergently and that these taxonomic groups have recruited different genes to bring about similar metabolic processes.

Threonine aldolase and alcohol dehydrogenase activities in Lactobacillus bulgaricus and Lactobacillus acidophilus and their contribution to flavour production in fermented milks

1983 ◽  
Vol 50 (3) ◽  
pp. 375-379 ◽  
Author(s):  
Valerie M. Marshall ◽  
Wendy M. Cole
Keyword(s):  
Alcohol Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Lactobacillus Acidophilus ◽  
Lactobacillus Bulgaricus ◽  
Flavour Compound ◽  
Threonine Aldolase ◽  
Fortified Milk ◽  
Alcohol Dehydrogenase Activity ◽  
Aldolase Activity ◽  
Acetaldehyde Production

SummaryCell-free extracts of both Lactobacillus bulgaricus and L. acidophilus demonstrated threonine aldolase activity, the end product of which was acetaldehyde, the major flavour compound of yoghurt. L. acidophilus also possessed an alcohol dehydrogenase activity capable of reducing acetaldehyde so that little yoghurt flavour was present in milks fermentation with this organism. Addition of threonine to fortified milk before fermentation with L. acidophilus increased acetaldehyde production and resulted in a well flavoured product similar to that of yoghurt made with L. bulgaricus. The contribution of these 2 enzymes to flavour production is discussed.

scholarly journals Characterization of an Escherichia coli K12 mutant that is sensitive to chlorate when grown aerobically

1978 ◽  
Vol 176 (2) ◽  
pp. 553-561 ◽  
Author(s):  
G Giordano ◽  
L Grillet ◽  
R Rosset ◽  
J H Dou ◽  
E Azoulay ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biosynthetic Pathway ◽  
Formate Dehydrogenase ◽  
Biochemical Characterization ◽  
Reductase Activity ◽  
Growth Conditions ◽  
Aerobic Growth ◽  
Benzyl Viologen ◽  
Genetic Lesion

Escherichia coli can normally grow aerobically in the presence of chlorate; however, mutants can be isolated that can no longer grow under these conditions. We present here the biochemical characterization of one such mutant and show that the primary genetic lesion occurs in the ubiquinone-8-biosynthetic pathway. As a consequence of this, under aerobic growth conditions the mutant is apparently unable to synthesize formate dehydrogenase, but can synthesize a Benzyl Viologen-dependent nitrate reductase activity. The nature of this activity is discussed.

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