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.

Inhibition kinetics for propionate degradation using propionate-enriched mixed cultures

1998 ◽  
Vol 38 (8-9) ◽  
pp. 443-451 ◽  
Author(s):  
S. H. Hyun ◽  
J. C. Young ◽  
I. S. Kim
Keyword(s):  
Phase I ◽  
Competitive Inhibition ◽  
Gas Production ◽  
Phase Iii ◽  
Utilization Rate ◽  
Inhibition Kinetics ◽  
Wide Range ◽  
Propionate Degradation ◽  
Acetate Utilization ◽  
Velocity Coefficient

To study propionate inhibition kinetics, seed cultures for the experiment were obtained from a propionate-enriched steady-state anaerobic Master Culture Reactor (MCR) operated under a semi-continuous mode for over six months. The MCR received a loading of 1.0 g propionate COD/l-day and was maintained at a temperature of 35±1°C. Tests using serum bottle reactors consisted of four phases. Phase I tests were conducted for measurement of anaerobic gas production as a screening step for a wide range of propionate concentrations. Phase II was a repeat of phase I but with more frequent sampling and detailed analysis of components in the liquid sample using gas chromatography. In phase III, different concentrations of acetate were added along with 1.0 g propionate COD/l to observe acetate inhibition of propionate degradation. Finally in phase IV, different concentrations of propionate were added along with 100 and 200 mg acetate/l to confirm the effect of mutual inhibition. Biokinetic and inhibition coefficients were obtained using models of Monod, Haldane, and Han and Levenspiel through the use of non-linear curve fitting technique. Results showed that the values of kp, maximum propionate utilization rate, and Ksp, half-velocity coefficient for propionate conversion, were 0.257 mg HPr/mg VSS-hr and 200 mg HPr/l, respectively. The values of kA, maximum acetate utilization rate, and KsA, half-velocity coefficient for acetate conversion, were 0.216 mg HAc/mg VSS-hr and 58 mg HAc/l, respectively. The results of phase III and IV tests indicated there was non-competitive inhibition when the acetate concentration in the reactor exceeded 200 mg/l.

Correlation of DNA adenine methylase activity with spontaneous mutability in Escherichia coli K-12

Gene ◽  
1984 ◽  
Vol 28 (1) ◽  
pp. 123-125 ◽  
Author(s):  
M.G. Marinus ◽  
Anthony Poteete ◽  
Judy A. Arraj
Keyword(s):  
Escherichia Coli ◽  
Dna Adenine Methylase ◽  
Spontaneous Mutability ◽  
K 12 ◽  
Methylase Activity

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 Kinetic mechanism of Escherichia coli isocitrate dehydrogenase and its inhibition by glyoxylate and oxaloacetate

1986 ◽  
Vol 234 (2) ◽  
pp. 317-323 ◽  
Author(s):  
H G Nimmo
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Isocitrate Dehydrogenase ◽  
Initial Rate ◽  
Potent Inhibitor ◽  
Competitive Inhibition ◽  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Coenzyme Binding ◽  
Inhibition Studies

The inhibition of Escherichia coli isocitrate dehydrogenase by glyoxylate and oxaloacetate was examined. The shapes of the progress curves in the presence of the inhibitors depended on the order of addition of the assay components. When isocitrate dehydrogenase or NADP+ was added last, the rate slowly decreased until a new, inhibited, steady state was obtained. When isocitrate was added last, the initial rate was almost zero, but the rate increased slowly until the same steady-state value was obtained. Glyoxylate and oxaloacetate gave competitive inhibition against isocitrate and uncompetitive inhibition against NADP+. Product-inhibition studies showed that isocitrate dehydrogenase obeys a compulsory-order mechanism, with coenzyme binding first. Glyoxylate and oxaloacetate bind to and dissociate from isocitrate dehydrogenase slowly. These observations can account for the shapes of the progress curves observed in the presence of the inhibitors. Condensation of glyoxylate and oxaloacetate produced an extremely potent inhibitor of isocitrate dehydrogenase. Analysis of the reaction by h.p.l.c. showed that this correlated with the formation of oxalomalate. This compound decomposed spontaneously in assay mixtures, giving 4-hydroxy-2-oxoglutarate, which was a much less potent inhibitor of the enzyme. Oxalomalate inhibited isocitrate dehydrogenase competitively with respect to isocitrate and was a very poor substrate for the enzyme. The data suggest that the inhibition of isocitrate dehydrogenase by glyoxylate and oxaloacetate is not physiologically significant.

scholarly journals Competitive inhibition and substrate activity of uridine diphosphate 6-deoxygalactose for Escherichia coli uridine diphosphate galactose 4-epimerase (Short Communication)

1973 ◽  
Vol 131 (2) ◽  
pp. 421-423 ◽  
Author(s):  
M. Spencer ◽  
P. Blackburn ◽  
W. Ferdinand ◽  
G. M. Blackburn
Keyword(s):  
Escherichia Coli ◽  
Short Communication ◽  
Competitive Inhibition ◽  
Uridine Diphosphate ◽  
Uridine Diphosphate Galactose

UDP-6-deoxygalactose inhibits the UDP-galactose 4-epimerase (EC 5.1.3.2) from Escherichia coli in a competitive manner with respect to the substrate UDP-galactose, giving Ki 1.3×10-3m. As a substrate for the enzyme, it is transformed into UDP-6-deoxyglucose, although the reaction stops before equilibrium is attained. Possible causes of this behaviour are discussed.

scholarly journals Effect of Indole Compounds on Vitamin B12 Utilization

Blood ◽  
1958 ◽  
Vol 13 (3) ◽  
pp. 239-244 ◽  
Author(s):  
JERRY DREXLER
Keyword(s):  
Escherichia Coli ◽  
Vitamin B12 ◽  
Mutant Strain ◽  
Indoleacetic Acid ◽  
Competitive Inhibition ◽  
Enzymatic System ◽  
Indole Compounds

Abstract Indole and indoleacetic acid are shown to inhibit the growth of a vitamin B12 dependent microorganism, a mutant strain of Escherichia coli. It is suggested that the mechanism of that inhibition may be a competitive inhibition of some enzymatic system necessary for the utilization of vitamin B12.

scholarly journals A Rapid Transglutaminase Assay for High-Throughput Screening Applications

2006 ◽  
Vol 11 (7) ◽  
pp. 836-843 ◽  
Author(s):  
Yu-Wei Wu ◽  
Yu-Hui Tsai
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Enzyme Inhibitors ◽  
Competitive Inhibition ◽  
Fluorescent Substrate ◽  
Highly Sensitive ◽  
The Family ◽  
Fluorescent Molecules ◽  
Inhibition Pattern ◽  
Guinea Pig Liver

Transglutaminases (TGs) are widely distributed enzymes that catalyze posttranslational modification of proteins by Ca2+-dependent cross-linking reactions. The family members of TGs participate in many significant processes of biological functions such as tissue regeneration, cell differentiation, apoptosis, and certain pathologies. A novel technique for TG activity assay was developed in this study. It was based on the rapid capturing, fluorescence quenching, and fast separation of the unreacted fluorescent molecules from the macromolecular product with magnetic dextran-coated charcoal. As few as 3 ng of guinea pig liver transglutaminase (gpTG) could be detected by the method; activities of 96 TG samples could be measured within an hour. The Km of gpTG determined by this method for monodansylcadaverine (dansyl-CAD) and N, N-dimethylcasein was 14 and 5 μM, respectively. A typical competitive inhibition pattern of cystamine on dansyl-CAD for gpTG activity was also demonstrated. The application of this technique is not limited to the use of dansyl-CAD as the fluorescent substrate of TG; other small fluor-labeled TG substrates may substitute dansyl-CAD. Finally, this method is rapid, highly sensitive, and inexpensive. It is suitable not only for high-throughput screening of enzymes or enzyme inhibitors but also for enzyme kinetic analysis.

scholarly journals The kinetics of hydrolysis of synthetic glucuronic esters and glucuronic ethers by bovine liver and Escherichia coli β-glucuronidase

1973 ◽  
Vol 133 (4) ◽  
pp. 789-795 ◽  
Author(s):  
J. Tomašić ◽  
D. Keglević
Keyword(s):  
Escherichia Coli ◽  
Kinetic Data ◽  
Glucuronic Acid ◽  
Bovine Liver ◽  
Kinetics Of Hydrolysis ◽  
Substrate Saturation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Ylacetic Acid ◽  
Optimal Ph

1. The relative rates of hydrolysis of synthetically prepared β-d-glucuronic esters [aglycone: benzoic acid, veratroic (3,4-dimethoxybenzoic) acid, indol-3-ylacetic acid and ethylbutyric acid], and β-d-glucuronic ethers (aglycone: phenolphthalein, p-nitrophenol, 3,4-dimethoxyphenol, 3,4-dimethoxybenzyl alcohol) by commercial preparations of β-glucuronidase from bovine liver and Escherichia coli were investigated. The rates of hydrolysis of all compounds tested were followed by measuring the formation of glucuronic acid under conditions which do not affect the glycosidic ester bond. 2. The pH profiles of the substrates in reaction with the enzyme from both sources were determined, and substrate-saturation curves at the optimal pH for each substrate were constructed; double-reciprocal plots of activity against concentration were linear. 3. Comparison of kinetic data indicates that neither the type of sugar–aglycone linkage, nor the aglycone structure alone can explain the observed Km and Vmax. values. 4. α-d-Glucuronic esters of benzoic and veratroic acid resisted hydrolysis by β-glucuronidase from both sources.

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