Phosphonic acid analogues of carbohydrate metabolites. Dihydroxypropylphosphonic acid. II. Substrate specificity of L-glycerol-3-phosphate : NAD oxidoreductase

1969 ◽  
Vol 47 (10) ◽  
pp. 992-994 ◽  
Author(s):  
Erich Baer ◽  
Darius J. Nazir ◽  
Hemendra Basu
Keyword(s):  
Enzyme Activity ◽  
Substrate Specificity ◽  
Phosphonic Acid ◽  
Inhibitory Effect ◽  
Phosphate Ester ◽  
Ester Bond ◽  
Structural Requirement ◽  
Nad Oxidoreductase ◽  
Carbohydrate Metabolites

The specificity of L-glycerol-3-phosphate : NAD oxidoreductase with regard to the phosphate ester bond of L-α-glycerophosphoric acid was investigated by means of L- and DL-dihydroxypropylphosphonic acid. The phosphate ester bond was found to be an essential structural requirement for enzyme activity. Neither L- nor DL-dihydroxypropylphosphonic acid has an inhibitory effect on the oxidation of L-α-glycerophosphoric acid by L-glycerol-3-phosphate : NAD oxidoreductase.

scholarly journals Potentiation effect of choline esters on choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase

1992 ◽  
Vol 284 (1) ◽  
pp. 153-160 ◽  
Author(s):  
Y B Kim ◽  
C H Jung ◽  
S J Choi ◽  
W J Seo ◽  
S H Cha ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Quaternary Ammonium ◽  
Acyl Chain ◽  
Requirement Analysis ◽  
Ester Bond ◽  
Choline Ester ◽  
Anionic Sites ◽  
Structural Requirement ◽  
Potentiation Effect ◽  
Choline Esters

The choline esters potentiated the choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase in proportion to the length of acyl group, although esters containing an acyl chain longer than the hexanoyl group exhibited a corresponding decrease in the potentiation. In structural requirement analysis it was found that both the quaternary ammonium moiety and the ester bond were important for the effective acceleration of choline-catalysed decarbamoylation. In general, the respective thiocholine ester was found to be more effective than the corresponding choline ester. Whereas the binding affinity (Ka) of choline in the decarbamoylation was not significantly altered, the maximum decarbamoylation rate (kr(max.)) of choline was greatly enhanced in the presence of choline esters or thiocholine esters. Along with the above observation, the isotope solvent effect, the effect of ionic strength and the antagonism studies demonstrate that the choline esters or thiocholine esters may interact with one of peripheral anionic sites, and thereby make the choline-catalysed decarbamoylation more favourable.

Sinapine Esterase I. Characterization of Sinapine Esterase from Cotyledons of Raphanus sativus

1979 ◽  
Vol 34 (9-10) ◽  
pp. 715-720 ◽  
Author(s):  
Gerhild Nurmann ◽  
Dieter Strack
Keyword(s):  
Enzyme Activity ◽  
Esterase Activity ◽  
Raphanus Sativus ◽  
Sinapic Acid ◽  
Inhibitory Effect ◽  
Ph Optimum ◽  
Diisopropyl Fluorophosphate ◽  
E 600 ◽  
Red Radish

Abstract From cotyledons of Raphanus sativus (red radish) an esterase activity which catalyzes the hy­drolysis of sinapine into sinapic acid and choline has been isolated. The enzyme, which has a near absolute specificity, is not analogous with any esterase described in the literature. The reaction has a pH optimum of 8.5 and the apparent Km is 1.95 × 10-5 m. The enzyme is relatively insensi­tive to both physostigmine (eserine) {Ki = 1.73 × 10-4 m) and neostigmine (Ki = 2 .1 3 × 10-4 ᴍ). Diisopropyl fluorophosphate (DFP) showed no inhibition and diethyl p-nitrophenylphosphate (E 600) only a slight inhibitory effect at 10-5 ᴍ, respectively. Choline (10-2 ᴍ) was inhibitory but acetylcholine (10-2 ᴍ) stimulated the enzyme activity.

scholarly journals Validation of an HPLC Method for the Simultaneous Quantification of Metabolic Reaction Products Catalysed by CYP2C11 Enzymes in Rat Liver Microsomes: In Vitro Inhibitory Effect of Salicylic Acid on CYP2C11 Enzyme

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4294 ◽  
Author(s):  
Salhab ◽  
Naughton ◽  
Barker
Keyword(s):  
High Performance Liquid Chromatography ◽  
Enzyme Activity ◽  
Salicylic Acid ◽  
Liquid Chromatography ◽  
Rat Liver ◽  
High Performance ◽  
Inhibitory Effect ◽  
Metabolic Reaction ◽  
Rat Liver Microsomes

The inhibitory effect of new chemical entities on rat liver P450 marker activities was investigated in a functional approach towards drug development. Treatment of colorectal cancer (CRC) and chemoprevention using salicylic acid has gained a lot of attention, mainly in the prevention of the onset of colon cancer. Thus, an in vitro inhibitory effect of salicylic acid on rat CYP2C11 activity was examined by using high performance liquid chromatography (HPLC). High performance liquid chromatography analysis of a CYP2C11 assay was developed on a reversed phase C18 column (SUPELCO 25 cm × 4.6 mm × 5 µm) at 243 nm using 32% phosphate buffer (pH 3.36) and 68% methanol as a mobile phase. The CYP2C11 assay showed good linearity for all components (R2 > 0.999). Substrates and metabolites were found to be stable for up to 72 hours. Additionally, the method demonstrated good reproducibility, intra- and inter-day precision (<15%), acceptable recovery and accuracy (80%–120%), and low detection (1.3501 µM and 3.2757 µM) and quantitation limit values (4.914 µM and 9.927 µM) for 16α-hydroxytestosterone and testosterone, respectively. Salicylic acid acts reversibly as a noncompetitive (weak) inhibitor with Ki = 84.582 ± 2.67 µM (concentration of inhibitor to cause 50% inhibition of original enzyme activity (IC50) = 82.70 ± 2.67 µM) for CYP2C11 enzyme activity. This indicates a low potential to cause toxicity and drug–drug interactions.

Glycoprotein Biosynthesis: Stimulation of N-Acetylglucosaminyltransferase Activity by Cytidiee 5′-Diphosphocholine

1972 ◽  
Vol 50 (10) ◽  
pp. 1082-1093 ◽  
Author(s):  
Sailen Mookerjea
Keyword(s):  
Enzyme Activity ◽  
Phospholipase C ◽  
Inhibitory Action ◽  
Inhibitory Effect ◽  
Nucleotide Sugar ◽  
Inorganic Pyrophosphate ◽  
Golgi Membranes ◽  
Cationic Detergents ◽  
Better Than ◽  
Stimulation Of

The stimulatory effect of CDP-choline on N-acetylglucosaminyltransferase activity is marked in rough microsomes but is almost absent in Golgi-rich membranes or in serum. The marked CDP-choline effect on the enzyme is evident even when the nucleotide–sugar substrate concentration is raised to near saturation. Diglyceride has an inhibitory action on the enzyme which is effectively reversed by further addition of CDP-choline. Of the other different lipid factors tested only CDP-ethanolamine has a stimulatory effect similar to CDP-choline. CDP-choline alone activates the enzyme better than Triton. CDP-choline and Triton, in different combinations of doses, show a marked synergistic effect. Cationic detergents do not activate the enzyme and inorganic pyrophosphate almost completely inhibits the enzyme activity. Phospholipase A has an inhibitory effect in the presence of CDP-choline. Phospholipase C, by itself, stimulates the enzyme activity. In the presence of CDP-choline, a higher concentration of phospholipase C partially abolishes the CDP-choline effect on the enzyme. Phosphorylcholine from labeled CDP-choline is rapidly incorporated into lecithin in the assay system used for measuring N-acetylglucosaminyltransferase activity. Capacity for lecithin synthesis is poor in Golgi membranes. However, lecithin synthesis is stimulated by adding exogenous diglyceride, but CDP-choline plus diglyceride failed to activate N-acetylglucosaminyltransferase in Golgi membranes. Finally, various possibilities have been discussed to explain the mechanism of action of CDP-choline on the enzyme.

Inhibitory effect of six herbal extracts on CYP2C8 enzyme activity in human liver microsomes

Xenobiotica ◽  
2014 ◽  
Vol 45 (5) ◽  
pp. 406-412 ◽  
Author(s):  
Ahmed A. Albassam ◽  
Mohamed-Eslam F. Mohamed ◽  
Reginald F. Frye
Keyword(s):  
Enzyme Activity ◽  
Human Liver ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Human Liver Microsomes ◽  
Herbal Extracts

UDP-Glucose: Flavonol 7-O-glucosyltransferase Activity in Flower Extracts of Chrysanthemum segetum

1997 ◽  
Vol 52 (3-4) ◽  
pp. 153-158 ◽  
Author(s):  
K. Stich ◽  
H. Halbwirth ◽  
F. Wurst ◽  
G. Forkmann
Keyword(s):  
Enzyme Activity ◽  
Specific Activity ◽  
Temperature Stability ◽  
Inhibitory Effect ◽  
Hydroxyl Group ◽  
Ph Optimum ◽  
Yellow Colour ◽  
Commercial Strain ◽  
Strong Inhibitory Effect ◽  
Chrysanthemum Segetum

Abstract The yellow colour of Chrysanthemum segetum petals is due to the presence of the 7-O-glucosides of quercetin and particularly gossypetin (8-hydroxyquercetin). In petal extracts of C. segetum an enzyme was demonstrated which catalyzes the transfer of the glucosyl moiety of uridine 5'-diphosphoglucose (UDPG) to the 7-hydroxyl group of flavonols with gossypetin and quercetin as the best substrates. Besides flavonols flavanones and flavones were found to be glucosylated in the 7-position. The pH-optimum of the reaction highly depended on the substrate used. With quercetin as substrate, maximal enzyme activity occurred at a pH of 8.25 and a temperature of 25 °C, but 7-O-glucosylation also proceeded at low temperatures. Studies on temperature stability revealed, that there was no influence on the glucosylation reaction up to 40 °C. Higher temperatures led to a loss of enzyme activity. Using gossypetin as a substrate a similar course of temperature stability was observed. Addition of Mg2+, Ca2+ and KCN slightly stimulated 7-O-glucosylation, whereas Co2+, Cu2+, Fe2+, Hg2+, p-hydroxymercuribenzoate and N-ethylmaleimide showed a strong inhibitory effect. Additional enzymatic studies were performed with the commercial strain " Stern des Orients" where gossypetin 7-O-glucoside is restricted to the inner parts of the petals. For enzyme extracts from both parts of the petals gossypetin was found to be the most attractive substrate. In comparison to quercetin (133.4 μkat / kg protein) an about three times higher specific activity of the 7-O-glucosyltransferase(s) was determined with gossypetin (382.1 μkat/ kg protein) as substrate, indicating that hydroxylation of quercetin in 8-position to gossypetin precedes 7-O-glucosylation.

scholarly journals Validation of an HPLC Method for the Simultaneous Quantification of Metabolic Reaction Products Catalysed by CYP2E1 Enzyme Activity: Inhibitory Effect of Cytochrome P450 Enzyme CYP2E1 by Salicylic Acid in Rat Liver Microsomes

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 932
Author(s):  
Hassan Salhab ◽  
Declan P. Naughton ◽  
James Barker
Keyword(s):  
High Performance Liquid Chromatography ◽  
Enzyme Activity ◽  
Cytochrome P450 ◽  
Salicylic Acid ◽  
Liquid Chromatography ◽  
Drug Interactions ◽  
High Performance ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Rat Liver Microsomes

Inhibition of cytochrome P450 (CYP) alters the pharmacokinetic parameters of the drug and causes drug–drug interactions. Salicylic acid been used for the treatment of colorectal cancer (CRC) and chemoprevention in recent decades. Thus, the aim of this study was to examine the in vitro inhibitory effect of salicylic acid on CYP2E1 activity in rat liver microsomes (RLMs) using high-performance liquid chromatography (HPLC). High-performance liquid chromatography analysis of a CYP2E1 assay was developed on a reversed phase C18 column (SUPELCO 25 cm × 4.6 mm × 5 µm) at 282 nm using 60% H2O, 25% acetonitrile, and 15% methanol as mobile phase. The CYP2E1 assay showed a good linearity (R2 > 0.999), good reproducibility, intra- and inter-day precision (<15%), acceptable recovery and accuracy (80–120%), and low detection (4.972 µM and 1.997 µM) and quantitation limit values (15.068 µM and 6.052 µM), for chlorzoxazone and 6-hydroxychlorzoxazone, respectively. Salicylic acid acts as a mixed inhibitor (competitive and non-competitive inhibition), with Ki (inhibition constant) = 83.56 ± 2.730 µM and concentration of inhibitor causing 50% inhibition of original enzyme activity (IC50) exceeding 100 µM (IC50 = 167.12 ± 5.460 µM) for CYP2E1 enzyme activity. Salicylic acid in rats would have both low and high potential to cause toxicity and drug interactions with other drugs that are substrates for CYP2E1.

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