scholarly journals Interaction of the lacZ β-galactosidase of Escherichia coli with some β-d-galactopyranoside competitive inhibitors

1979 ◽  
Vol 177 (1) ◽  
pp. 145-152 ◽  
Author(s):  
R. S. Thomas Loeffler ◽  
Michael L. Sinnott ◽  
Brian D. Sykes ◽  
Stephen G. Withers
Keyword(s):  
Escherichia Coli ◽  
Competitive Inhibition ◽  
Phenolic Hydroxy Group ◽  
Bivalent Metal ◽  
Transverse Relaxation ◽  
Competitive Inhibitors ◽  
Inhibition Constants ◽  
Increasing Temperature ◽  
Phenolic Hydroxy ◽  
Average Position

1. The location of the bivalent metal cation with respect to bound competitive inhibitors in Escherichia coli (!lacZ) β-galactosidase was investigated by proton magnetic resonance. 2. Replacement of Mg2+ by Mn2+ enhances both longitudinal and transverse relaxation of the methyl groups of the β-d-galactopyranosyltrimethylammonium ion, and of methyl 1-thio-β-d-galactopyranoside; linewidths are narrowed by increasing temperature. 3. The Mn2+ ion is located 8–9Å (0.8–0.9nm) from the centroid of the trimethylammonium group and 9Å (0.9nm) from the average position of the methylthio protons. 4. The effective charge at the active site was probed by measurement of competitive inhibition constants (Kio and Ki+ respectively) for the isosteric ligands, β-d-galactopyranosylbenzene and the β-d-galactopyranosylpyridinium ion. 5. The ratio of inhibition constants (Q=Ki+/Kio) obtained with 2-(β-d-galactopyranosyl)–naphthalene and the β-d-galactopyranosylisoquinolinium ion at pH7 with Mg2+–enzyme was identical, within experimental error, with that obtained with the monocyclic compounds. 6. The variation of Q for Mg2+–enzyme can be described by Q=0.1(1+[H+]/4.17×10−10)/1+[H+]/10−8). 7. This, in the theoretical form for a single ionizable group, is ascribed to the ionization of the phenolic hydroxy group of tyrosine-501. 8. The variation of Q for Mg2+-free enzyme is complex, probably because of deprotonation of the groups normally attached to Mg2+ as well as tyrosine-501.

scholarly journals 7-Deazapurine 2'-deoxyribofuranosides are noncleavable competitive inhibitors of Escherichia coli purine nucleoside phosphorylase (PNP).

1998 ◽  
Vol 45 (3) ◽  
pp. 755-768 ◽  
Author(s):  
A Bzowska ◽  
Z Kazimierczuk ◽  
F Seela
Keyword(s):  
Escherichia Coli ◽  
Purine Nucleoside Phosphorylase ◽  
Modified Nucleosides ◽  
Purine Nucleoside ◽  
Preliminary Screening ◽  
Nucleoside Phosphorylase ◽  
E Coli ◽  
Potent Inhibition ◽  
Competitive Inhibitors ◽  
Inhibition Constants

A series of 7-deazapurine 2'-deoxyribofuranosides were synthesized according to already known procedures and their substrate and inhibitor properties with purified E. coli purine nucleoside phosphorylase were examined. In agreement with previous findings, substrate activity was not detected for any of the compounds tested. Most of the nucleosides showed weak inhibition in the preliminary screening, i.e. at a concentration of about 100 microM. However some combinations of 6-chloro, 6-amino or 6-methoxy substituents with bulky hydrophobic groups at position 7 of the base and/or chloro, amino, methoxy or methylthio group at position 2 markedly enhanced affinity of such modified nucleosides for the E. coli enzyme. The most potent inhibition was observed for two nucleosides: 6-chloro- and 2-amino-6-chloro-7-deazapurine 2'-deoxyribofuranosides that show inhibition constants Ki = 2.4 and 2.3 microM, respectively. Several other compounds were also found to be good inhibitors, with inhibition constants in the range 5-50 microM. In all instances the inhibition was competitive vs. the nucleoside substrate 7-methylguanosine. Inhibition constants for 7-deazapurine nucleosides are in general several-fold lower than those observed for their purine counterparts. Therefore 7-deaza modification together with substitutions at positions 2, 6 and 7 of the base is a very promising approach to obtain competitive noncleavable inhibitors of E. coli PNP that may bind to the enzyme with inhibition constants in the microM range.

In Silico Prediction and Validation of Oxygen-Regulated Protein N-myc Downstream Regulated Gene 3 and Virtual Screening of Competitive Inhibitors of L-Lactate as Therapeutics

2019 ◽  
Vol 16 (6) ◽  
pp. 637-644
Author(s):  
Hongyu Cao ◽  
Yanhua Wu ◽  
Xingzhi Zhou ◽  
Xuefang Zheng ◽  
Ge Jiang
Keyword(s):  
Active Sites ◽  
Competitive Inhibition ◽  
Hydrophobic Effect ◽  
3D Structure ◽  
Amino Acid Residues ◽  
In Silico Prediction ◽  
Hypoxic Response ◽  
Drug Candidates ◽  
Competitive Inhibitors ◽  
Extracellular Regulated Protein Kinases

Background: N-myc downstream regulated gene 3 (NDRG3) is a newly discovered oxygen-regulated protein which will bind with L-Lactate in hypoxia and further activate Raf (rapidly accelerated fibrosarcoma)-ERK (extracellular regulated protein kinases) pathway, promoting cell growth and angiogenesis. Methods: Competitive inhibition on the binding of NDRG3 and L-Lactate may be potentially a useful strategy for the repression of hypoxic response mediated by NDRG3. The threedimensional (3D) structure of NDRG3 was built by using homology modeling for its crystal structure was not available. Then, L-Lactate was docked into NDRG3, from which we knew it bound with amino acid residues Gln69, His183, Asn189, Ala72 and Pro66 of NDRG3 in the most possible active sites. Approximately 3000 compounds have been virtually screened and the 6 topranked compounds were selected as reference molecules to analyze their interaction relationships, which illustrated that some of them might form electrostatic interaction with Glu70 and Asp187, π-&π stack with Phe75 and Tyr180, hydrogen bonds with Gly71 and Asn189, hydrophobic effect with Ala72 and Ile184. Results: Novel molecules were designed through structural optimization of the 6 top-ranked compounds and subsequently their ADMET properties were predicted. Conclusion: These molecules may be potential drug candidates for the suppression of hypoxic response mediated by NDRG3 and targeted therapy for hypoxia-induced diseases.

Di- and tripeptide N-alkyl- and N-aralkyl amides as chymotrypsin inhibitors

1988 ◽  
Vol 53 (11) ◽  
pp. 2877-2883 ◽  
Author(s):  
Evžen Kasafírek ◽  
Irena Šutiaková ◽  
Michal Bartík ◽  
Antonín Šturc
Keyword(s):  
Methyl Ethyl ◽  
Competitive Inhibitors ◽  
Inhibition Constants ◽  
Chymotrypsin Inhibitors

Two competitive inhibitors of chymotrypsin, Glt-Ala-Ala-Leu-EtPh and Glt-Ala-Ala-Pro-NH-EtPh, were synthesized and their inhibition constants Ki were determined. The Ki-determination was carried also with a set of peptides of type X-(Ala)nNH-Y, where X is 3-carboxypropionyl- or 4-carboxybutyryl-, n is 2 or 3 and Y is methyl, ethyl, diethyl, isopropyl, propyl, butyl, isobutyl and 2-phenylethyl. Chymotrypsin inhibition was observed only with peptides containing an aralkyl residue whereas peptides with an alkyl are without any effect. Glt-Ala-Ala-Leu-NH-EtPh shows the highest Ki-value (80 μmol l-1).

S-Adenosylethionine as an inhibitor of tRNA methylation

1969 ◽  
Vol 47 (5) ◽  
pp. 561-565 ◽  
Author(s):  
B. G. Moore ◽  
R. C. Smith
Keyword(s):  
Escherichia Coli ◽  
Preliminary Data ◽  
Kinetic Data ◽  
Competitive Inhibition ◽  
Inhibition Kinetics ◽  
Inhibition Reaction ◽  
Inhibition Pattern ◽  
Methylase Activity

S-Adenosylethionine was shown to inhibit the methylation of tRNA by S-adenosylmethionine. Lineweaver–Burk plots of kinetic data suggested that the inhibition was competitive. Another known inhibitor of tRNA methylation, adenine, also exhibited competitive inhibition kinetics. A derivative of S-adenosylethionine, ethylthioadenosine, also inhibited the reaction and displayed a competitive inhibition pattern. These data were obtained using Escherichia coli K12W6 as a source of methyl-deficient tRNA and methylase enzymes. Preliminary data indicate that S-adenosylethionine is even a better inhibitor of rat methylases.Methylase activity of ethionine-fed rats was elevated, which suggested that the inhibition reaction with S-adenosylethionine and the increased methylase activity may proceed by two different pathways.

Effects of Hemin and Heating Temperature on the Mutagenicity and Lipid Oxidation of Pork Batter during In Vitro Human Digestion with Enterobacteria

2018 ◽  
Vol 82 (1) ◽  
pp. 93-101
Author(s):  
HYEONG SANG KIM ◽  
DA YOUNG LEE ◽  
SUN JIN HUR
Keyword(s):  
Escherichia Coli ◽  
Antioxidant Activity ◽  
Lipid Oxidation ◽  
Large Intestine ◽  
Antioxidative Enzymes ◽  
Antioxidant Activities ◽  
Heating Temperature ◽  
Lactobacillus Sakei ◽  
Increasing Temperature

ABSTRACT The objective of this study was to determine the effects of hemin and heating temperature on the mutagenicity and lipid oxidation of pork batter during in vitro human digestion with enterobacteria. The mutagenicity and lipid oxidation of pork batter increased in the presence of hemin and with increasing temperatures from 60 to 80°C by 17.9 and 23.0% and by 54.6 and 21.2%, respectively. However, the pork batter mutagenicity decreased by 6.09% during in vitro human digestion, whereas lipid oxidation increased by 19.4%. The antioxidant activities of pork batter decreased with hemin and increasing temperature but gradually increased during in vitro human digestion, especially in the large intestine, regardless of the type of enterobacteria (Escherichia coli and/or Lactobacillus sakei). These results indicate that hemin and temperature are closely related to mutagenicity in pork batter, and in vitro human digestion with enterobacteria could reduce mutagenicity possibly owing to the increase in antioxidant activity by antioxidative enzymes released by enterobacteria.

The dynamic behaviour of nitrifying Activated sludge systems influenced by inhibiting wastewater compounds

1995 ◽  
Vol 31 (2) ◽  
pp. 115-124 ◽  
Author(s):  
O. Nowak ◽  
K. Svardal ◽  
P. Schweighofer
Keyword(s):  
Activated Sludge ◽  
Treatment Process ◽  
Dynamic Behaviour ◽  
Competitive Inhibition ◽  
Nitrification Inhibition ◽  
Peak Loads ◽  
Inhibitory Compounds ◽  
Competitive Inhibitors ◽  
Nitrification Process ◽  
Activated Sludge Systems

More or less severe nitrification inhibition was observed in several pilot and full-scale activated sludge plants treating industrial wastewaters. In order to control the treatment process under inhibiting conditions, extended nitrification models have been developed on base of the ‘Activated sludge model No. 1’. In the case of temperatures between 25 and 30°C, the nitrification process has been expressed as a two-step reaction with nitrite as intermediate. Model elements for competitive and non-competitive inhibition as well as for biodegradation of the inhibitor were added, if required. The dynamic behaviour of the investigated activated sludge systems indicates that there are biodegradable non-competitive inhibitors. Operational as well as simulation results show that nitrifying activated sludge plants may become acclimatized to inhibitory compounds but have to be protected from peak loads of both nitrogen and inhibitory compounds.

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